it could have just been a conflict in the drivers upon boot up or something. I don't think it would be a virus or trojan. rebooting is always the best first step. if you right click on my computer the go to property's the device manager and you see a yellow dot with and exclamation point in it that's a drive conflict. if rebooting it does not work you will need to update the driver. do you let windows update regularly?

glad it all worked out in the end