Is Winamp Agent running?
If so, try disabling it to see if this was the cause?
(Prefs -> Agent: uncheck all 3 options)
Are all the tracks in your playlist MP3's ?
If so, all I can think of right now is:
Prefs -> Input -> MPEG Audio Decoder -> config -> Decoder tab
Uncheck: CRC Checking
(Though this option isn't enabled by default)
Can you give us any more info about the error message?
Where is it actually coming from? Surely not Winamp?
Is it an error regarding the RAR archive, or the MP3 being played in Winamp?
Exact wording please!
What ZIP/RAR program is it?
Does it have anything in the options related to CRC Checking being enabled?
More info about CRC Check here:
btw, you missed out your OS in the specs list. It always helps to know!
Don't know if this is worth mentioning, but I'm making it a policy to bring it to the attention of all Winamp users with SBLive cards: