The problem is on the machine you are attempting to connect to, not the machine where you see the error message.
On the computer SHARING OUT the disk, check the event viewer for an event ID 2011.
Usual fix :
You need to fix a parameter called IRPStackSize
On the machine SHARING OUT the disks:
Set the IRPStackSize back to the default (15 )
Perform the following steps:
1. Start the registry editor (e.g., regedit.exe).
2. Navigate to HKEY LOCAL MACHINE\SYSTEM\CurrentControlSet\
Services\lanmanserver\parameters.
3. Double-click IRPStackSize
(or if this registry setting doesn't exist,create it of
type DWORD and ensure the case is correct).
4. Change the base to decimal, set the value to 15, and click OK.
5. Reboot the computer.
Norton AV is usual suspect for breaking it.
There's a KB article about this, too. You may have missed it, because it's applicability has not been updated to include XP:
Antivirus Software May Cause Event ID 2011 (Q177078)
http://support.microsoft.com/default.aspx?scid=kb;EN-US;q177078