add discount does nothing [SOLVED]

Hi,
I just installed v.1.5.1.3. It's on a linux server with a recent install of Apache. I wanted to experiment with having different prices for different groups. First I added some groups in users>usergroups, no problems. Next I went to catalog>products, found a product then clicked on edit and then discount. I see the button that says "add discount". When I click on it absolutely nothing happens. Am I missing something? Is there anything I can check before I give up and just reinstall the whole thing?
Thanks!

make sure you don't have javascript blocked. When you click the button a row should appear with several text entry boxes in it.

Javascript is enabled. I just realized that under special, the "add special" button doesn't work either. The others seem to work, like "add Attribute" and "add Image".

OK, nevermind. I decided to reinstall and it's working now. Must have just had a corrupted file somewhere.