Driver's SQLAllocHandle on SQL_HANDLE_DBC failed

hi guys.

i'm using microsoft odbc and i close and open a lot of connections
through my code at a regular basis. for some reason, sometimes, not
always, i get the following error when i try to open a new connection
to the DB: "ERROR [IM005] [Microsoft][ODBC Driver Manager] Driver's
SQLAllocHandle on SQL_HANDLE_DBC failed".

on the db side, the postgresql error log shows nothing abouy this.
any ideas why this is happening?

my postgresql version is: 7.4.6

Thank You, amir