mm: MmInsertRmap bugcheck when connecting USB audio device

Created an attachment (id=7723)
Log file of bugcheck with backtrace

Revision: 56660 (dbgwin build + a few unrelated USB fixes)
VM: VBox 4.1.14 (Win7 x64 host)

Attaching a "3D Sound" USB audio device (basically just speaker and mic jacks) causes a MEMORY_MANAGEMENT bugcheck in MmInsertRmap. See the attached log.

The problem happens while loading hidusb.sys. It is pretty well reproducible, although not perfectly (log of a successful run follows).
The VM has 3 GB RAM (thus the high physical address), but the same happens with only 512 MB (with an accordingly lower physical address).