Mystic,
I completely understand...This is the first version Xpress XT USB, actually have been using for about 15 years. I know they were plagued with a lot of issues....but to tell you the truth mine is actually a stable one. I have not had many issues in using it and I have used it quite a bit with a full setup. x64 Yes I had driver issues in the past...to tell you the truth this problem in earlier version of Dimension and Sonar would cause BSOD and badly stuck audio engine. That has since went away with updating Sonar and also newer versions of the Motu x64. However the same issue exists in Sonar/DPRO....Cakewalk handles it better it seems.....instead of a BSOD it will hard crash, or I can do work arounds.
I am blaming Dimension Pro Mystic, I've actually had this problem since Dimension first came out...might be interrelated...but every other piece of software, including other Cakewalk interfaces do not have this issue. I actually used Rapture in the exact same manner last night for quite awhile....and worked perfectly. The moment I start using Dimension I will start crashing Sonar, the DPRO standalone, and start losing audio engine. So yes it could be related to the MOTU, however Dimension Pro should not respond this way. I really think they have a MIDI input problem in the code which allows the driver to bring it to it's knees....I would say bad MOTU...but no other software seems to respond in this way.
That's too bad though you had soo many issues with your Xpress XT. I remember having issues when I first had in my system...that all changed though. Besides being a culprit in the DPro issue it works perfectly.
The biggest issue I had was sync to multi-devices using Sonar...I believe I found it sends sync to all ports if you select one in Sonar. I was having multiplier effect going which caused me erratic MIDI behavior. Using ASIO (WDM I get timing issues, over time and instability) and only selecting to send MIDI Sync to one device cured this for me.