Hi Mark Jones,
It seems that the issue occurs while using applications from Windows 8 ‘Start’ screen. Does this happen while using a specific application or it happens randomly with any application? If it’s with a specific application, you can try to uninstall and reinstall it.
Please ensue that the Windows is up to date. Refer to the following link to know how to manage Windows Updates: http://bit.ly/ZFkqLG
Although, you have upgraded to Windows 8 just now, you may also create a new user account with administrative privileges and check if you still face the issue while using the new account, please check the link: http://bit.ly/10h7xsr
Hope this helps. Please reply with the findings. I would be glad to assist further.