[MonetDB-users] (Jdbc?) concurrency issues

Hi, I'm implementing a bit of a consumer-producer application in Java using the JDBC driver. When I use transactions in the producer & consumer, I'll frequently get the "ERROR: COMMIT: transaction is aborted because of concurency conflicts, will ROLLBACK instead" error. Not quite sure why this keeps happening. It's not like the same row is modified concurrently. The same *table* is (insert in one thread, vs delete in another). Could this be the cause of the problem? And more importantly, how do I get around this? thanks a bunch, - Bram