Which version of Overachiever are you using?
0.65

What steps will reproduce the problem?
1. Seems to somehow be related to pets despawning/dying/respawning/being resurrected but I can't exactly pin down an EXACT cause

What is the expected output? What do you see instead?
Simple tainting that seems to be caused by something in overachiever.

Do you have an error log of what happened?
Yes. Here's a pastebin of my taint.log http://pastebin.com/A1pxsLEs

Does this problem occur when all other addons are disabled? If not, use the process of elimination and report where the addon conflict lies (including the version of the conflicting addon).
As I'm having difficulty reproducing it, I can't really provide any info here.

Please provide any additional information below.
Seems to happen most of the time to pet-using classes, but also happens in raids.