That's an odd one, and as likely to be elated to your operating system as to Photoshop. First thing to do is restart your computer. If the issue is still there, try resetting Preferences (hold down Shift Ctrl Alt or Shift Cmd Opt immediately after starting Photoshop.
If you still have problems come back, but let us know what operating system you have.
Thanks. I rebooted and checked out preferences, but still having the problem. I'm on Mac OS X, v. 10.5.8.
OK. I am going to have to let someone who knows Mac try and help you then. How old is your Mac? We have seen glitches with Mavericks, but you are a way behind that.
I did find these old threads:
Thanks for the links.
The computer is running Mac OS X, v 10.5.8; computer bought new in 2008.
Experimenting a bit, it seems that if I click on the drop down button on, say, Opacity or Flow, then hold the cursor down while moving the cursor over the slider arrow, I can at least usually move the slider arrow right or left to adjust those percentages (as long as I don't let go of the cursor)
More problematic is that as soon as I click on the size/hardness/brush type window, no matter what tool I'm using, the window disappears. I think this is only happening with that size/hardness window, and no others (I can still adjust size using the bracket keys).