Internal Server Error on installation

When I attempt to install the plugin, I get an Internal Server Error before the plugin is even uploaded. The zip file never even makes it to the server.

I've seen this before with my own plugins before, but have never really figured out what caused it because it wouldn't happen on all servers, only some. Now it's happening with a WPMUDEV plugin as well. Anyone have any ideas what causes this? I'm on WP 3.3.2