Deadlock problem

Hello.

I have an multithreaded java application using postgresql. I am using UR mode (handling locking internally)
and wa shoping to have no problems with locks.
But now I have locking porlbme where there is only one thread calling posgresql and locking in wait.
Looking at pg_lock I can see a lot of locks each holding exclusive a transaction (other two fields are empty).
And for one transaction there is one PID holding Exclusive Lock and another waiting for shared lock for
same transaction.
I suppose that this means that I've first used connection object from one thread and this thread pid (linux
x86-64) took exclusive lock and now another thread tries to use same connection and is going into lock.
Am I correct? If so, why this exclusive locks are help while there no other queries executed? Or does this
mean I can't use same connection object from different threads?

С уважением,
Виталий Валериевич Тимчишин,
Технический Директор
ООО "Голден Технолоджис"
http://www.gtech-ua.com