PT unable to communicate with HUI

[pasanta]

I use a Mackie Control Universal (original MIDI model, not the more recent USB model) with my 002r. I keep getting the "unable to communicate with HUI" message and it drops the connection to the MCU. This started some time ago with the upgrade to 7.4. I had hoped moving to 8 and OSX 10.5.8 would get rid of it but it hasn't. I've done the usual troubleshooting steps; trashing prefs, databases, etc. It was infrequent at first, but the last few days has been pretty constant. The last change to my system would have been the move to PT8 some months ago. Here's what else I've tried to narrow down the problem without success:

• moved the midi connections off the 002r to a MAudio midi interface
• moved the midi connections to a MOTU Express 128
• changed all midi cables
• removed any midi related drivers or files from system and audio/midi setup utility that don't pertain to just PT and the MCU

Now..... I also have an old d24 system. The MCU works fine on it as does a PC running Samplitude. If I switch to a Mbox2, and attach the midi there, it again runs perfect. It also runs perfect on the other midi interfaces as long as the MBox2 is used. It would seem that somehow taking the 002r out of the loop solves the problem. How or what could be the cause of that? The audio runs fine; it's the midi that gets dropped even when the 002r is not serving as the midi connection. Firmware is current; all other components and software is current.

What haven't I thought of?

MacPro (8 core)
OSX 10.5.8
PT LE 8.01
MCU (firmware 2.12......as current as there is)