I upgraded from Mac OS Mavericks 10.9.5 to Mac OS Yosemite 10.10.1 and have issues with Mac App Store.
If I search for an item, I get results, but if I click a result, I get a blank page, whatever the app's page I want to see.
As you can see, the classic app background doesn't even appear.
I do not experience this issue on a fresh install of Yosemite in another mac, so I did bought my app on the other mac and used the search results's menu to install it on the right one, but that's quite tricky.
I tried to reboot, to reset the PRAM and other stuffs I seen over the internet, but didn't found any good answer.