I have 2419 and H+ has not worked on any build up to this point. Last nite I just gave up My symptoms exactly matched yours)and used PowerDVD 3.0, that seemed to play very well.
Sigma product of mine has been problematic from the beginning, but until DVD support/acceleration got built into Video cards in a fundamental way, and along with faster processors, it ruled. I still like the card. When using ME or W2K, I got an error hardware subvendor ID missing, and until I ran the hwsubid.exe I got from Sigma, it would not work there either. Hmmm, maybe I will try that tonite. (probably won't help, but, hey).
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Thanks and Best Regards