Here's one possible explanation. Plus some off topic tangents to make us all feel at home.
http://forums.digitalspy.co.uk/showthread.php?t=1197836
Short answer- Blu-ray can play back at 24 frame per second film frame rate, DVD tends to round up to 25 so pitch rises a bit with the faster playback rate. In these cases, Blu-ray is generally fixing an earlier problem of the digital age, fudging film frame rates to sync with video scanning rates, that DVDs are bound by. It's complicated, but might explain discrepancies such as you're describing.
But since I didn't actually listen to your examples, I'm not sure how much pitch discrepancy we're talking about here. But I meant well.
