Well tvengr, you were right. At first I figured it might be more of an issue unrelated to the card, after trying different ones, because I couldn't see how that would affect the internal physical workings like button function. Then, after the last attempt I surmised, along with you, that the buttons worked while powering up, apparently before the card is "detected", but then problems started as soon as the card was "in use" and scanning. I've had minor weird things happen in the years I've owned this unit and they have all been micro card related. Those dang rascally micros...
So, after trying a couple different new micros I finally got a Sandisk 8G microsd HC class4 to work. For now everything seems to be back to normal.
Thanks for all the help and advice.