1.5.0.2 is the version of Firefox
I've yet to upgrade mine--it's a customized build for Linux ;)
Anyways, on most platforms, you're going to want to select the Edit menu and click on Preferences
If you run Windows, select the Tools menu and click on Options.
In the Preferences (Options) dialog, select Content
Under there, the first listing should be "Block Popup Windows" -- on the right hand side, there should be a button that says "Allowed Sites." Click on it.
When the dialog box appears, type in "www.freerepublic.com" in the space and click Close. This takes you back to the main Options box. Click Close.