Drop connection to XP share

Hi there

I have a XP Pro on laptop and Vista Ult on PC. I can access shares
both ways. The thing is that I can't copy any files to XP folder,
because after "calculating time to copy files" the msg pops-up that
connection has been closed. All priviledges to access the folder are
set to Everyone -> Full Access both share and NTFS rights.
When I restart computer and access my laptop from XP installed also on
my PC, everything works fine.

Thanks for any advices