thread on the Vita discussion forum. Sony is focused on fixing this. "We are aware of the issue, and will resolve it as quickly as possible," a Sony spokesperson told Edge.
It appears Minis purchased outside from the PS Plus free-game deal work fine on the Vita, according to the thread. So, uh, take that, PS Plus members. We bet you're really regretting buying into that awesome exclusivity deal with Sony right about now, because you can't play your Minis and the problem will probably be fixed really soon. Yeah.