You might look into your motherboard/pci hardware.  I was having similar
issues (lots of wm0 device timeouts, but none of the dropped
configuration) and a change of motherboards was the fix.  I'm now running
a km400-based board from Shuttle, and it's completely fixed all of my
problems.  Basically the PCI bus on the old board wasn't fast enough to
keep up with the device, and it was causing the timeouts.

Tim