samba - Apr 2013 - "database or networkerror" message by access using a backend at a samba share

hi,

since yesterday i'm using ms access mdb files as frontend (started by 
win clients) and linked to mdb backend files located in a
samba share (opensuse 12.3).
But problems: sporadic occurs a "database or network connection" error
on the client (popup from msaccess)

but the network is still alive and the share/mdbs reachable

the backend mdbs are in use by about 20 users, which client = random, 
which time = random

on the win client: close message, restart frontend and its going well

today: 3 errors at 3 different clients

looks like a timeout problem or ...?