Ok, so I have this wood elf who started off with a 50% resistance to disease, then she became a vampire and added another 100% resistance to disease, and somehow she caught a disease. Can someone explain how that happened?

This has been happening to me lately. Both disease and poisons. Must be a glitch introduced in a recent patch or Dawnguard.

That's what I figured, just wasn't 100% sure. Doesn't affect my game too much, was just curious if anyone else had this happen.