Pull Down Menu text delay

The menu with the down arrow to the right, that drops downs a series of
choices or desired entries - is that the "drop down" or "pull down" menu?
Doesn't matter - my problem is that the text within that drop down window
doesn't appear instantly - there's a second or two delay, then it shows up.
It's annoying.

Running Vista Ultimate. This wasn't a problem until recently. Cause?
Solution?