App store will not work.

No matter what I do, the app store will not let me download anything. I am using a 21 in iMac, running OS 10.6.8. I've tried logging out, deleting the cache, repairing disk permissions on the HD, etc.

Every time I click to "Get" something or "Purchase" something, the button goes gray as it is depressed, and it doesn't do anything. The app store doesn't freeze, I can still click other things and move about the page. However, the button that I clicked to "Purchase" or "Get" something stays pushed in, until I manually refresh the page.

Is there any way to reinstall the app store? I do not have the boot up disk for this computer. I do not have any 10.6.8 boot up disk. I just bought this computer, used. Please help.