Cannot access all folders in shared network drive

Hi, I cannot access all the folders in a shared network drive. When I try to
open certain folders is says folder not available. If you hover the mouse
over the folder it says it is empty (it isn't!).
I am using windows xp pro sp3 on a wireless laptop and trying to accessing a
shared drive on windows vista premium sp1. I cannot understand how I can only
access some of the folders in the shared drive and not all. Is there a limit
to the amount of folders u can have in a shared drive? or a limit to the
amount of files?