I don't think it's a WMP 10 bug, I've never had this problem before, but other people have. Since I never tried to play the problem files using WMP 9, I wouldn't know for sure.
WMP 10 DOES have it's bugs, and I am thoroughly disgusted with it. things like a video not playing again if you stop it while in full-screen mode (unless you leave full-screen first) or the fact that the exit button in full-screen does not work 80% of the time. I could go on to list a dozen more things that I hate about it, but it's more or less irrelivant to the subject... back on topic...
I'll look at trying the gspot solution, though I don't fully trust software without looking further into it.
I don't have the DivX player installed - just the codecs. all other DivX compressed videos seem to work fine. What I need it the codec for use in WMP.