iPod Nano stuck in "lock" mode

My iPod nano seems to be stuck in the locked position - not "locked" because I created a password for it, but it simply displays the lock symbol in the upper left corner regardless of how many times I flip the switch back to what should be "unlocked." Because of this, I have no control over it. When I disconnect it from my PC, the screen turns black and I cannot operate it. Battery is fully charged. Have tried soft reset many times, restore several times - no luck.

Suggestions??????

Thanks in advance.