This can go wrong in two places... on the device end and the android end.
When hooked up to USB, there should be in the status notification section
of android a little USB icon (looks like a trident/pitchfork). You need to
click on that and make sure it is set to the USB mass storage mode. By
default it is in "windows media server" mode or "none".

On the other end, it could just be a matter of not automatically mounting
the drive. You can open up a terminal and type 'sudo mount -a' to muont all
connected devices and filesystems specified in fstab. It is also
possible you could need to write a udev rules file for the tablet, but I
don't think you need that unless you are trying to run through the android
debug bridge server (where you are communicating through your device in a
terminal).

dont know if this would work, but could u plug it in then search for drivers?

The problem often encountered with 3g devices is the on-board windows
drivers. This memory needs to be unmounted for Ubuntu to find the device
behind it. I don't know if this will help with your device but it is
worth a try.

I've had the same problem with my Xoom from day one (March 2011). I've
read some solutions but they were exceedingly complicated and the one
that worked didn't succeed in the second machine I tried it on.

I think there is a need for something to be added to (K)ubuntu to make
the Xoom connect. I don't know any more than that but I sure wish some
member of the community would figure it out and make it available. If
it works on Windows there is no reason I know of why it can't be made
to work on Ubuntu... please!

I can connect in the other direction, over the USB cable, using a File
Manager on the Xoom, but connecting using the PC would be a bit easier
(full size keyboard, big monitor etc.).

If you can connect and transfer files then the Xoom is being detected
by Ubuntu and it's a question of how to get the file manager to know
that it's there. Can you access through terminal ?

LAC> I can connect in the other direction, over the USB cable, using a
LAC> File Manager on the Xoom

--

How would I access it through a terminal. df doesn't show it and it
isn't showing up in /media.

That is in spite of trying to follow the instructions here
www.linuxtechworld.com/index.php\
emid=230

They are not easy to do, and I could have made a mistake but frankly
I'm not about to go down that path again - more trouble than it is
worth.

Pretty comprehensive instructions and yes a little on the convoluted
side so you could have made an error somewhere. Interesting that the
Xoom can access Ubuntu and presumably see the file system / navigate
etc. Maybe there's enough difference between the Kubuntu file system
and Ubuntu for the instructions to fail, though don't see anything
that would be that different. Could be an error in the config file
modifications needed.

At least you can transfer files between Ubuntu and your Xoom even if
it's not quite as easy as it could be

I'm satisfied but keeping an open mind...

folowing google's instructions
developer.android.com/.../device.html>

you need to reset permissions after creading the rules file:
chmod a+r /etc/udev/rules.d/51-android.rules

You may also need to create a group, specify it at the end of the line
in rules file, and add your user account to that group in Kubuntu.

As an aside, I'm not sure why those instructions have you entering the
vendor ID for a google device as well as motorola... I don't quite
get that.

As you are trying to figure this out, two programs to add to your xoom
that I enjoy very much on my usb-cripled droid:

andFTP
http://www.lysesoft.com/products/andftp/> allows to connect to ftp or
ssh server from device. supports secure/encrypted protocol
swiFTP
http://code.google.com/p/swiftp/> Runs an FTP server from your device
that can be connected to from any ftp client on a local network. can
be set up on the fly with dummy passwords and only runs when you
activate it.

I also like ConnectBot and full keyboard. ConnectBot does
remote login via ssh/telnet and full keyboard supports control characters.
Great for remote administration. Having the control characters allows you
to run a text editor and change config files as needed.