Cannot Access Shared External USB Hard Drive

I am having an issue accessing a shared external USB drive in a
workgroup.
Both computers are running XP PRO sp2.
Computer 'A' can share a folder on the internal 'C' drive and computer
'B' can read/write to it without a problem.
Computer 'A' can also share either the complete external USB hard
drive or a folder.
I have configured the share to allow other users to read and write.
The share name is visible to computer 'B', but when I click on it, a
message pops up indicating that I do not have sufficient permissions.
No filenames are displayed.
No firewalls are enabled on either computer
The username and password that I am using on computer 'b' are the same
on computer 'a'.

Thank you in advance for all assistance.