How to fix panel that is suddenly too dark.

[joe at actionline.com]

Just installed Linux Mint 13 (which am finding to be quite good) but
suddenly the panel became very dark and when I click on the clock and
device notifier, the backgrounds are black so I can't read them.

Can't imagine what could have caused this change as I did not (knowingly)
make any changes.

Here are a couple of screen-shot examples:

http://www.upquick.com/temp/clockblack.jpg
http://www.upquick.com/temp/notifierblack.jpg

What do I need to do to get rid of this blackness?