I use a SanDisk Titanium drive with my Ubuntu machine, and it works just fine.
I've never used the other brands you've mentioned, so I can't say whether it's a
manufacturer-specific problem.

it's nice to know that at least some drives work :-)

Of course, I'm not discounting the possibility that I'm the problem,
rather than Ubuntu ;

I've had no trouble with Sandisk -- thumb drives,
anyway -- &, in all the years I've been running Linux, the only
manufacturers of drives I've had no trouble with are Maxtor.
While every other drive had given me one problem or another in
Linux, I've used a number of different Maxtors in various distros
of Linux, & they've all worked beautifully.

Plus, they're often less expensive than others.

Are any of your USB drives are connected
at the boot up? The other question comes to mind is that have you mount each
one? If you change them here and there while Ubie is on. You are getting Ubie
confused on what you want to do. Some times my Micro Flash from my phone will
not work all the time when the system is on. If I boot up with the card in. No
problem. It reads it and I can go one with life and sit back do my mojo.

The Seagate and Philips were both connected at boot, but not the WD -
but having now rebooted with the WD plugged in, it makes no difference.

Just for the record, I have no problem with flash cards or thumb drives
- apart from the fact that no matter what I do, I cannot make thumb
drives bootable (I know that it can be done as I have a Mandriva thumb
drive which boots just beautifully).

All these drives are formatted as ext3 - do you think it would make any
difference if I switched to another file system?

OK, I've been sent the following two links about the Seagate FreeAgent
drive, which explain the problems I'm having and a way to solve them.
Now, all I need to do is find a Windows user so I can sort it out :-)

www.theinquirer.net/gb/inquirer/news/2007/12/06/*seagate*-snubs-*linux
*www.theinquirer.net/gb/inquirer/news/2007/12/11/*seagate*-issues-workaround-*li\
nux
*
I've also made some progress with the WD Passport drive. By formatting
it to FAT32 and writing a couple of udev rules, I can get the drive to
work - but ONLY if I sudo into Nautilus. If I try to access the drive
as a standard user, the owner and group are both set to root - even
though I have explicitly set the group to plugdev - and I can't do
anything with the drive, but if I sudo into Nautilus, the group is
suddenly reported, correctly, as plugdev and I can access the drive.

Now I'm kicking myself. I've got the Philips drive to work after all.
How? Changed the USB cable.

A faulty ****** cable!

I shall now go and feel very embarrassed.

This sort of things happens too often. Your problem made me look in-
line for an affordable cable tester. I regret that most are a few
hundreds of dollars.

I did find this one that is almost temptingly low enough to
get........... $46....

http://www.jdr.com/interact/item.asp?itemno=CT-RU

I think having a tester is still a good idea and will look for DIY
solutions to make a tester. Ringing the few lines in a cable should
be a simple enough matter to rig some sockets, led's, and a battery.

If anyone finds a $5 tester, Please let me know.

I know, it just made me so mad that I never thought of something so
*simple*. I was so locked into the tech solution that it never occurred
to me to check the cable - it was my mother's idea to check. She's now
feeling *so* smug.

Anyway, fixed the Seagate now, as well. The article I referenced gave
me the idea to run a cron job every 5 minutes to access the disc, just
to keep it going. It's a bit of a dirty hack, but it works, so I don't
care. I now have two out of three of my drives working, just the WD
Passport to go and I'll be a very happy chappy

I reformatted the drive to ext3 and got exactly the same problems as
before (owner:group reported as root:root rather than the root:plugdev I
had set them to). I sudo chgrp'd /media/Portable (where I have the
drive mounted) and was told I didn't have permission to change the
group, so I sudo'd into Nautilus, navigated to /media/Portable,
right-click on a bare part of the file list window and was allowed to
change the group. Why I should be allowed to do it this way and not
from the command line, I have no idea - but it worked, so I'm not
complaining

I'm using a LaCie 500GB USB disk to make backups. One problem I had
was with a slightly older computer which only had USB 1.1 ports. While
transferring big files it sometimes gave errors, making it unreliable.
After I installed a USB 2.0 PCI card, it was OK, and offcourse much
faster as well.

Yes, my PC has USB2.0 ports and the WD and Philips drives are running
direct off the PC, while the Seagate is running off a USB2.0 hub (which
may, or may not, be part of the problem). In fact, this *is* kind of
part of the problem with the Seagate - after it spins down, when you try
to access it again, the drive itself comes back as USB1.1, even though
it's a USB2.0 drive. Windows can handle it, Linux can't.