Vista - cannot logon network attached storage

i have two lacie ethernet disk servers attached to my router/network. one is
a 1TB server and the other is a 2TB server. each say they have a windows xp
based OS. i have been able to access their shares easily when i was using
xp. now that i have switched to vista ultimate, i cannot access the 2TB
server. i can still access the 1TB no problem. i have spoken to lacie
support and they said,

"Vista changes the way the devices are addressed over the network. It is
likely a problem with the way Vista is attempting to identify the unit
(likely it is sticking the machine name in front of the user name, but not
telling you it is doing this.)

There is no way to fix this for a mapped drive from the drive's side of
things. There may be a way to correct it by changing settings in Windows
Vista. You may wish to contact Microsoft for help with this. "

this seems true. when i enter my username/pass and get the error, i see
that the username has been changed to "computername\username" rather than
just "username"

any ideas as to how to stop vista from adding the computer name to my
username?