Windows XP - can't log on to Samba

i've got a linux redhat server, 2 winXP and an apple. the apple can log
on to the samba, no problem.
the 2 windows computer could log on as well, everything was smooth, but
suddenly i get those "not accesible, you might not have permission...."

when i try to log on through the workgroup rather than the short cut,
it states that there is a dublicate name on the network and i should
rename the computer and try again. well i tried a few times, same
statement. i must admid, i might had the same name, log in etc.

but i've changed it, and the samba is running fine. sometimes i can log
in with my XP, than it is fine for a few days and suddenly, same thing
happens.

any logical explanations?

any help appreciated.

Dimitri