Thankfully, we can't reproduce the problem under Winamp 5.31 (or 5.32 internal beta).
Are you also using some old version of Winamp?
Are you also using CA eTrust AV Corporate Edition?
Using DirectShow for decoding MP3 is not really a recommended workaround
(no metadata support, ie. ID3 tags will not be used/read, no replaygain support, no 24bit playback support, no portable player support, no transcoding support, etc etc).
There's no known conflicts/issues with Winamp and ZoneAlarm.
I've used ZA for years with no problems whatsoever.
As for CA Antivirus, well, I'm using CA EZ AntiVirus and don't have any problems, although I did add the Winamp folder to the RealTime Exclusion List in CA config (Virus Scanning > Scan Settings > RealTime Scanner > Exclusions/Modify).
Prior to that, I noticed that CA was constantly scanning winamp's config files (winamp.ini, studio.xnf, gen_ml.ini, etc) which caused a minor slowdown, but no crashes for me.
I assume that even the version of CA eTrust AV which comes with ZA must have its own separate config and RealTime Exclusion List, ie. separate to ZoneAlarm config...?
Other than any of that, as I said, we can't reproduce the problem.
Other things you can try...
Try a clean install
of Winamp 5.31
Make sure 'Fast Layer 3 EQ' is unchecked in in_mp3 config > decoder tab
Make sure 'CRC Checking' is unchecked.
Checkmark 'Show average bitrate on vbr files'.
Apply the DirectSound Output tweaks
(if not already applied)
ie. select soundcard as Output Device, check/unheck 'allow hardware acceleration', checkmark 'enable cpu-usage control'
Remove any 3rd-party plugins
(which are more than often responsible for over 80% of all problems reported on these forums).