Can't figure this out... procedure conflicts

Thanks in advance to anyone who can shed some light on this, or tell me 
where to look for some help.


I start two processes - P1 and P2.  Both should take about X minutes when 
run alone.

Process P1 finishes in X+Y minutes - not surprising because there were two 
running.

However:
  Process P2 is still running after 2X+Y (actually *much* longer) minutes.

More facts:
Both of these processes update the same table - but different records.  
There are many Update statements in both processes.

Help!
Tim

Oracle 9.2.0...
Red Hat Advanced Server 2.5
Intel (Dell) 2-processor (Xeon)
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