Error renaming file or folder

I get that error with the text: Cannot rename <filename>:
it is being used by another person or program. Close any
programs that might be using the file and try again.
This happens when I try to change the file on computer A
from computer B. After this occurs, I can't do anything
with the file on computer A either, until after I reboot.
I set access with simple access to allow changes, but
that didn't work, so I changed to ?not simple? access and
set permissions from there, but still no luck. Computer
A has XP Pro, while computer B has XP home.
Any ideas?