Directx/decoder problem

[Grasshopper]

I've been experiencing an odd problem recently. I'll probably submit a tech support request, but I thought I'd ask the experts on this forum before I bug George. This problem predates my upgrade to v5. It's on a dedicated Client box running XP Pro and the nVidia decoders.

Here's the problem. After the box has been running for a while and several shows have been played back, asking it to play back a show triggers a "DirectX error", advises me to upgrade or reinstall DirectX. (Sorry, exact wording escapes me, and I can't reproduce the error at will). Frequently I can get the error to go away by going into Setup, selecting a different decoder, and trying again. Sometimes, I need a reboot. After reboot, it works fine, until it doesn't.

Any tips or insight? I'm fully updated with the latest DirectX, I think.