there may have been a change in the audio codecs that are used, i found out the longway around that this can happen and gives simialr symptoms to the ones you describe.
How to find out - goto control panel-system-hardware-devices look for sound video game controllers, and expand. look for audio codecs right click and properties, hit the properties tag at the top, look for windows media audio codac, highlight and select properties, check the button use this audio codac, make sure or change the priority to 1,, ok etc all the way back out. and hopefully bob will be your mothers brother.
good luck
rickity