Hi Allan,
Yup it was a USB issue - but it was changing the extender cable not the Belkin adapter that finally fixed my issue. Belkin get some stick for poor driver support, they are not the chipset maker for their products so after a bit of searching I found that compatible 64 bit drivers are available for the adapter from MCT:
http://www.mct-us.com/downloadfiles/....98.130315.zip
All is stable again now.