I/O hang on Server 2008

[Hortnon]

I've had a problem for a LONG time with VirtualBox on my Server 2008 R2 host. After some amount of time, anywhere after initial startup, disk I/O will completely stop for my VM's. Then the VM's start to get unpredictable and will hang some processes but not others. However, the VM never actually crashes and errors aren't reported by the guest OS. I've had this problem on Solaris, Linux, and Windows guests.

This is what it looks like inside the guest after the I/O has hung:



When the guest starts showing that wavy line the console output freezes unless you move the mouse over the window. Also notice how much network traffic the guest thinks there is on that graph.

This is the host's view of the same time period:



Host:
Server 2008 R2 with current patches
Intel Xeon E5620 dual socket
60GB RAM
AHCI storage enabled
VirtualBox 4.2.10 (I've had this issue going back several releases of VirtualBox)

This particular guest:
Solaris 11.1 with newest support patches and guest additions
6 CPU with PAE/NX,VT-x,Nested Paging, PIIX3 chipset
64MB video RAM
SATA AHCI controller with one virtual disk and I/O cache enabled (I/O cache on/off doesn't appear to make a difference to the problem)