when i plug a thumb drive with music in my 2010 maxima-it has begun to skip and is unintelligible along with the display freezing--after about three minutes i hear three beeps and the display resets to normal--the display freezups happens in all modes. is this the beginning to something far worse?

Well, I've had sort of MP3 player gremlins before and for me it was the cable from my iPod to the head unit. If you have other cables, try using one of those for a while and see if the issues persist.

also affected are thumb drives with music or audio books

Well, I have seen the USB plug on a radio become loose, provide sporadic connectivity and finally become detached from the many times a USB cable has been plugged in and unplugged. It's unfortunate when that stops working. If you're into electronic repair, the socket can sometimes be soldered back.

If the display flickers and such with all modes, then there's another issue I think. Possibly just the power supply like a shorted hot wire or loose ground wire. Beeping and resetting could all be related to that. You'd have to get into the dash and check some wires to diagnose that. Hmm, ya know, USB has power in it's wires as well. Maybe it's all tied together by a power supply issue.

Perhaps it's all just loose connections. Maybe you could remove your whole stereo, then put it back in and re-seat each connector and hope that fixes things. You know, turn it off, unplug it, plug it in, turn it on and hope works for a lot of electronics.

Ultimately, you made need to replace the thing and could look at used units or aftermarket solutions. Good luck. Tunes are very nice to have for a drive.