Try changing the FW driver. While Avid recommends the Legacy driver. it never works here. The TI Compliant driver works fine. You also may have an incompatible FW controller in your new 'puter. Posting a Sandra report will usually show that, and a $50 SIIG FW card will usually solve that issue
info on the Sandra report here:
Help us Help You - READ THIS Before Posting!
****remember to NEVER hot-patch the FW cable****