Samsung's Blackjacks, newer-gen PDAs, are facing a quiet recall. AT&T, in conjunction with Samsung, have opted to recall the units for replacement. An undisclosed number of the units manufactured during a four-month period late last year and early this year apparently had a manufacturing flaw in the antenna design. The flaw would eventually cause the antenna to come loose. Unlike exploding batteries, however, it seems the worst this defect could result in is a phone that can't maintain connectivity to a cell tower.
If you happen to be using a Blackjack and are noticing a lot of dropped calls or weak signal, therin could lie your problem. You can read the advisory on the Cingular forums.