Postmaster taking 100% of the CPU

Postmaster's been spinning at 99/100% for a few hours.

trying to get an idea what would have caused it.

I'm on PG 8.3.5 linux.

Here's the gdb output (I'm not really all that gdb savvy, so if something else would let me know)
0x08281959 in textin ()
(gdb) bt
#0 0x08281959 in textin ()
#1 0x082c3d9f in InputFunctionCall ()
#2 0x081755dd in ?? ()
#3 0x081755dd in ?? ()
#4 0x08174fd3 in ExecEvalExprSwitchContext ()
#5 0x081890cd in ExecSubPlan ()
#6 0x08174ae1 in ?? ()
#7 0x08175040 in ExecQual ()
#8 0x0818322c in ExecHashJoin ()
#9 0x08174680 in ExecProcNode ()
#10 0x08185f1d in ExecNestLoop ()
#11 0x081746b0 in ExecProcNode ()
#12 0x0817ebbb in ExecAppend ()
#13 0x081745c0 in ExecProcNode ()
#14 0x081873b1 in ExecSort ()
#15 0x08174650 in ExecProcNode ()
#16 0x081875a6 in ExecUnique ()
#17 0x08174560 in ExecProcNode ()
#18 0x081873b1 in ExecSort ()
#19 0x08174650 in ExecProcNode ()
#20 0x081724c3 in ExecutorRun ()
#21 0x082133e3 in ?? ()
#22 0x082147a9 in PortalRun ()
#23 0x082111f1 in PostgresMain ()
#24 0x081e363d in ?? ()
#25 0x081e464f in PostmasterMain ()
#26 0x08198906 in main ()

Thanks

Dave