Error 5002 when trying to look at iTunes Plus

I just bought a new MBP, and since I used my education discount, I got a $100 gift card to use in the App Store/iTunes/etc. I have a bunch of songs I bought back when iTunes had DRM, so I was going to use this money to upgrade some of those purchases to iTunes Plus. However, whenever I click on "iTunes Plus" under Quick Links, I get a popup telling me that I can't access iTunes Plus because "Unknown Error 5002 Ocurred"

I've looked up the problem, and I've tried things like changing/resetting my billinb info, re-installing iTunes, and resetting my internet connection, but I have not had any luck so far. Does anyone know how to solve this?