PowerDVD + Filters Problem

Fron time to time I convert DVD's to mpg 4 format for playback on the PSP using either Nero Recode or InterVideo's "IvideoToGo for PSP". When trying to play the MP4 files with PowerDVD i get the following error message " PowerDVD + Error Code: 80040218 - No combination of filters could be found to render the stream". I am sure in the past PowerDVD did play these files fine. I can playback these files with NeroShowtime but its a Demo I am using, however this tells me I have the mpeg4 decoder needed to play these files installed. Any ideas what might be going on here and what I need to do to fix it. I am reluctant to install the klite codec pack or similar software as these packs can sometimes cause more issues than they solve.