Subject "lock time-out on wait transaction" when trying to DropDatabase

I get an exception "lock time-out on wait transaction.. object aaa.FDB is in use" when i try to drop the table using "FbConnection.DropDatabase(ConnectionString)".
It doesn't happen all the time, only when I access the DB a lot.

I closed all the connections before dropping the table ('ConnectionPoolsCount' was 0),
And I even tried using "FbConnection.ClearAllPools()" before dropping the table,
but it didn't work.

I tried to search a solution in the group history but I had no success,
Any one knows how can I solve this problem?
Is there a way to see who is using this object?

Thanks, Idan.