The only other thing I can suggest is to try a Selective Startup, which can help identify whether a background application is the cause:
- Press the Windows key
- Type ‘msconfig’ and select ‘System Configuration’
- On the ‘General’ tab, select ‘Selective Startup’
- Deselect ‘Load startup Items’
- Reboot your PC
If the issue no longer occurs after having performed the Selective Startup, try re-introducing your programs one-by-one to determine which is the culprit.