Stoik video Converter cannot open file problem

[mersiung]

Hi, I try to convert WMV to AVI using Stoik video converter, and I convert the audio to MPEG Layer 3, but it always said "CANNOT OPEN OUTPUT FILE". But if I change the audio to PCM it works fine.
What is the problem?? Should I install some plug-ins for MPEG Layer 3 conversion udsing Stoik?? Thanks.