Deadlock

While updating database (7.1.3)  thro' JDBC I get a deadlock error :

Exception Message: ERROR:  Deadlock detected.
See the lock(l) manual page for a possible cause.

As far as i can see I am not doing anything which can cause such a thing, everything is pretty straight forward.
SometimesI get:
 

 Cannot insert a duplicate key into unique index db_security_desc_object_id_key

I've looked at the code and these things shouldn't be happening, I am sure the mistake is mine but don't know how to go
aboutdebugging it. It happens only sometimes.
 

I do have unique key constrains on the table.

Any help will be appreciated.

-Nikhil
PS: how do i lookup all the constraints for a table in postgres?