Kernel panic after FreePBX 13 Upgrade

It's a filesystem problem, what the problem is I can't say, presumably between the virtualized kernel and the underlying hardware. Try another Virtualization method (KVM would be solid, perhaps even a virtualbox under your windoze, but Microsoft are a little dumb as yet about native VM's and I am sure Schmooze have better things to do than work around MS ) as a rough guess, turn off disk cacheing and enable disk write-backs if those are options.