M6 will not shut down

I've run into an interesting problem. My M6 is presently displaying a photo and a series of squares. None of the keys respond. Holding down the power and >>| has no effect. The manual does not address this problem but says if there is a problem turning the unit on, remove and replace the battery. I'm not certain how to open the case without voiding the warranty (I purchased it about a month ago). Any ideas?

Try press and hold the Enter button for about 10-20 seconds until the screen go off. A soft reset should help on this. Then you should be able to turn on your player normally.
If SL version, press and hold the Play button for about 10-20 seconds instead.
Hope this help.

Thank you very much for responding. Unfortunately, at the time, none of the buttons were responding. Now the M6 is completely dead (won't take a charge, won't turn on). As McCoy would say on the old Star Trek "It's dead, Jim".

Where is My Zoo when we need him...

You properly need DFU tools to revive your player:
You can follow this guide:
Guide: Fixing your "Bricked" Player

Just remember to search on your problem before your post. It's so easy to find help around here.