Ok, i think i might have stumbled upon a possible fix - at least its working for me so far.
First - plug in your usb cable to your pc & fon
Go into the settings>wireless and network>tethering and portable hotspot
click on USB tethering (this will start the service) and u will see a blue icon appear
now take the cable out of the fon
The tethering service icon will disappear and the tethering service will stop. I have been messing with my phone for 30 minutes and trying to get that tethering message to come up again and it hasnt. I have not rebooted the fon to test whether this fix is a resolved solution or its a quick fix. Let me know if it works for you.