Flex and WSJTX disconnection of CAT Interface

Hi all, I have an ongoing issue with WSJTX and Flex 6600 (I believe) CAT control interface. If my PC is left idle for some time, or if I come out after a few hours of not using PC, then changing bands within WSJTX will no longer change the radio, in fact, the PC just makes an error sound but no error is actually displayed suggesting the window has become somewhat modal, but in fact its not modal at all and is receiving decodes and can TX also, you just cannot change bands using the WSJTX band selector. Restarting WSJTX solves the issue immediately and restores full control. I have disable USB power options, I have no screen savers, power options are so that my displays turn off after 15 minutes but PC never hibernates or shuts down. Generally speaking, I rarely suffer the issue of the TX audio not working in WSJTX but it does happen on some occasions, but this issue with WSJTX disconnecting from CAT happens every day many times after the PC is left alone for a while. Now in fairness, I have only just made the changes to the USB idle state where I have disabled it so this MAY have resolved the issue, time will tell. I am just wondering if anyone else has same issue and has figured out what the cause is. Thanks, de Adam VK2PW