I recently ran into a similar issue with a 3.7 BCM 400. The VM was down, but all the sets worked fine. The LEDs were still flashing from a reboot days before they called me. I gave it a full cold boot, no more flashing LEDs, but also no VM. No response from the console port either.

It turns out that there is a problem with the DSPs or something similar. You have to remove the power cord for AT LEAST 15 minutes. After that, the system will fully boot and the VM will work again. The system even booted up very quickly this time!

This is a strange one that had me stumped. :bang:

Have Fun,
Wayne