Why can I no longer move files to or from my external drive?

Hello all :?

Apologies for the length of this post, but I'm using this as a last resort - I've already determined quite a lot about the drive's behaviour (I think) so I wanted to put it all down here to give others as full a picture as possible. Moderators, please let me know if I should cut this down or.. I dunno, anything. And please help?!

The salient points:
- I'm almost completely new to Linux
- I'm using an AA1 running Linpus
- I've been through a few tweak+tip lists and have enabled the rightclick menu from the desktop
- I've used add/remove software to install some games, educational packages and, most lately, bittorrent clients - I got Transmission, Bittorrent and Deluge (quickly decided to use just Deluge).
- the external drive in question is a WD 250GB My Passport, and it has a vfat filesystem

The problem started after the Passport was removed from the AA1 a few times without being unmounted (thanks to a crappy loose fit at the drive-end of the USB cable) while Deluge was running, with the external drive as the file destination. I'd immediately plug it back in and the AA1 seemed to have no problem picking the Pasport up and resuming all DLing of files to it straight away. Then it happened again and Deluge seemed to lose all file info for most of the torrents and began checking them. It would take *forever* to recheck directories for files I'd already part-DLed, returning 0% for some I *knew* were nearly finished before the problem started, and giving me messages like
"torrent paused: disk write error, open failed: '.... avi'. Read-only file system" and
"torrent paused: disk write error, open failed: '... .pdf'. No such file or directory"
even when the torrent in question was brand new (i.e. had just been added, and so the file - but not the directory I was saving it to - had just been created). Nothing is DLing now except for torrents which are creating files on the Acer's own file system, so as far as I can see all the problems stem from its failing to open / save to the Passport drive.

Ok, I thought, so much for DLing then. Now, however, I find I can't transfer files to and from the Passport, or delete files from it. I can read everything - I can use VLC to watch .avi, and .m4v files stored on the external, read documents and listen to mp3s - but I can't move anything. After trawling forums and googling for days, it seemed there might be a chance of moving small files, so I tried moving a few pairs of .jpgs (just kilobytes in size) and .m4vs (~70-80 MB) from the Aspire's own file system. Some success, I get maybe 3 or 4 moved onto the Passport, and then the next attempt might either be immediately refused and an input/output error quoted:

Failed to write data to "/media/My Passport/... ... .jpg" (Input/output error).

or it might get part of the way through the transfer (or even right to the end) before it tells me no, or it might tell me nothing and just freeze the file manager (that's Thunar, right?) at which point I can't even get access to the Aspire's own file system. Then I have to either wait til that sorts itself out, or try and get the Aspire to sleep and remove the drive while it's doing so or, if it won't sleep or even turn off (which it's done once or twice) I've resorted to just holding down the power button and forcing it off. When I restart the machine and plug in the Passport again, there's never *any* problem mounting it, but there's no guarantee the files I just moved onto it will be there, or they might be there but 0KB in size. I've tried moving just a couple and then stopping before I get the input/output error messages, instead trying to unmount the Passport, but I'm always told 'a process' is preventing the Passport from being removed. After 10-20 minutes I'll try again and can remove it no problem, but again the files I moved onto it mightn't be there when I go back. Bizarrely, there's more chance they'll be there if the Passport's been unplugged from the Aspire overnight - literally, if they've 'had a break' from each other! - but only the first pair I tried to move will be there. The last time, they were there only in name, size 0KB, and somehow i was allowed to replace the 0KB .m4v with the original 76MB one from the Aspire - although I thought it had frozen again, it resolved itself quite quickly and now the file is there. However, when I tried to replace the .jpg file, dialogue window after dialogue window appeared asking me if I wanted to replace the file - it seemed to initiate a loop. I eventually answered no and the loop stopped, so I thought I'd delete the 0KB .jpg file and then I could copy+paste the original one into that folder without creating a replacing problem. BUT of course it can't be deleted, cut or renamed!

Despite all this, the Passport works FINE in the old house PC downstairs, which is running XP (home, I think). Is this to do with permissions? I've tried a few permissions changes too, using alt+F2 to open a command ... box?! (sorry, my terminology's probably allll over the place!) and typing in
sudo thunar
to set myself up as the root user, clicking on My Passport and then opening the Properties dialog boxes on the drive itself and on folders to which I save/DL video, music or pdf files. In each case, when this problem started with Deluge, I found the owner was user and the permission was read only; I was able to change this to read and write for the folder to which I store video files, but it just wouldn't change for the music and document folders! I'd change the selection, I'd be asked if I wanted to apply this to all subfolders etc, I'd select yes and the dialogue box would appear shaded out. Now this is what happened when I did the video folder, and I just waited it out, but for the other two I'd wait and wait but it never resolved - eventually I just had to cancel it.

Sorry if there's much too much info here, but I have no idea what's going on here and, thus, what'll be useful for solving the problem. This WD Passport is the only really portable drive I have - I've got a Seagate 500GB one, but it's much bigger and requires plugging into the mains to work. There's rarely a place to do that when I have to use an external drive up on campus, which i do all the time because the Aspire seemingly can't handle the wireless broadband set-up up there. The Uni's tech guys tried for a month to sort it out, and the best they connection they could manage to rig up still gets 'lost' every half hour and then you have to restart the Aspire to get online again - sometimes 3 times in a row. So to manage a session downloading journal pdfs or getting the lecture ppts off the intranet etc. for longer than about 20 minutes I have to use a campus cluster computer, DL the files to an external drive (the extremely portable Passport) and then plug *that* into the Aspire. In other words, I *can't* have the Aspire and the WD passport not communicating like this! Can anyone help?

[there's something else I noticed at the start of all this - I couldn't dl an actual, working .torrent file on the Aspire (still working with the Firefox 2 it came installed with) - these files wouldn't start a torrent in Deluge. If I DLed the exact same .torrent file onto the Passsport using the XP PC downstairs instead, and then plugged it into the Acer and tried it in Deluge, no problem. Has anyone *any* idea what *that's* about either?!?!]