Multiple listener running (hanging) on the same port //weird..

Hi there,
today we encountered a strange problem regarding the listener process. (multiple process with the same listener name.. :-( )
versions: rdbms/listener 10.2.0.2
OS: AIX 5L 5200-09-04
so; from the process list of the AIX:
594032 991330 0 03:43:18 - 0:00 /orabinp/product/ora10g/bin/tnslsnr LSNRprod -inherit
991330 1 0 Mar 04 - 29:17 /orabinp/product/ora10g/bin/tnslsnr LSNRprod -inherit
as you see the 2nd listener was initiated from the "original" listener, (the parent ID is 991330)
the lsnrctl status, stop commands were hanging, the lsnr processes were terminated with -USR2 signal. lsnr start was ok, after this the application was able to connect.
resolution took around 3 mins, but there is a need to have a root cause analysis. usually when you want to start an already running listener,it results in a "TNS-01106: Listener using listener name 'LISTENERname' has already been started".
during this double operation there were no connection available (it is clear from listener.log)
Anyone had this issue?
Any comments welcome and highly appreciated.
p.s.
(oracle version 10.2.0.2 - first question -is it a known bug?- I have not found it in a bug list.. the db will be patched/migrated to 10.2.0.3 at next available downtime)

Virtual PC can do it, but it's not free. I think VMware as well, but likely not free. Actually, it seems you can evaluate VMware:
http://www.vmware.com/download/

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Multiple listener running (hanging) on the same port //weird..

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