[popwiz]

When I click on a menu item, the menu won't stay open. I'm used to seeing the open menu after I click, and I could move the mouse left and right to see corresponding menus. Now, I have to keep the mouse "clicked" in order to see it. I release the button and the menu disappears. Happens in OSX (10.2.8) an all applications.
This is a huge pain.
I can't find any preferences or options that correct this.

[SupahCoolX]

If you click and hold for a second, the menu will close when you release the mouse button (this is the old-school, traditional way of using menus on a Mac).
To have the menu stay open (called a "sticky menu"), just click and quickly release the button- just like a regular single-click on a button/icon/etc.

[Chuckit]

I haven't tracked down the cause, but I have seen this. It appears to be a strange 10.2 issue, and it may have something to do with Microsoft Word (that's the only common denominator I could find — all the computers that had it were running Word). Anyway, a restart fixes it for me. Logging out and back in probably would have the same effect, but I like to fsck whenever a computer is acting funny anyway.

[popwiz]

Thanks Chuck.
Restarting fixed the problem. I guess the fact that I didn't try that outs me as an idiot. I'm still curious as to the cause.