We have been investigating this issue as multiple customers - with varying flavors of Epson devices (scanners and printers) have been affected by this problem. Some were seen to "not work at all", others would "print, but only when you logged off" and other rather random weird behavior.
It currently looks like this is a problem in the way the Epson device driver actually behaves - it actually tries to start working before announcing it is ready to start, and as a result the virtual driver basically gets stuck. Since this is a generic Epson driver for printers and scanners then the same root cause affects multiple usb devices.
We have a potential fix in the pipeline to accommodate this odd Epson behavior. So hopefully we can get a fix for this out soon.
watch this space....
cheers
peterB