It has been a long time since I used Forms, but the situation sounds peculiar. I also haven’t worked on Oracle version 8 in a whaile.
The only thing I can imagine that would cause a hang – would be an insert in progress for the same primary key. I can duplicate the hung insert, but Oracle 9i let me drop the synonym while the two sessions were fighting over the insert. ;^> Perhaps that was different in version 8.
Sometiimes when a session gets killed, especially over a db link, the background operation can “live on”. It should time out after a while,or you could try bouncing the remote database.
I hope this helps.