Access 2000 and ODBC driver

Hello,
I have writen an application with ms-access 2000 as frontend for postgres. Normally it works well, but each time
when i have openend a form in my frontend and im doing nothing for some time (the pc goes into powersaving) i can't
work again with my form. I can't close it, i can't go to the next record --nothing. The only thing i can do is press ctrl-alt-del
and then kill the access-task.
What the hell is it?
My configuration is:

- Access 2000 (with .mbd or mde version of my frontend)
- Postgres 7.0.2
-ODBC driver 6.500
-MDAC 2.5

options in Postgres ODBC :

driver:

KSQO enabled
Recognize unique indexes enabled
Text as LonVarChar enabled

rest disabled

Connection:

Row Versioning enabled

rest disabled

Thanks for your help !