***** What steps will reproduce the problem?
It occurs in random battlegrounds, but it happens quite often in Wintergrasp.  I believe it happened to me a couple times during a PvE raid as well, so it's possible it has something to do with raids.  I can't figure out specifically how to reproduce it though.

***** What is the expected output? What do you see instead?
Several bars will be visible when they aren't supposed to be, e.g.: I have no target, but I can see a health bar, partially transparent.

***** What version of the product are you using?
3.2.11

***** Please provide any additional information below.
http://img188.imageshack.us/img188/6647/uifuckup2.jpg
http://img41.imageshack.us/img41/1269/uifuckup.jpg

The bar off to the left is my pet, which isn't visible when I'm mounted.  However, it along with the target's power bar, cast bar, and the target's target is visible, even when I don't have anything targetted.  Once this happens, it just "sticks" until I reload my UI.  If I try targetting something (as the second image shows me targetting myself), you can see the semi-transparent bars still "stuck" there.

These are the mods that I have installed/enabled:
Pitbull
Pitbull_Aura
Pitbull_CastBar
Pitbull_HealthBar
Pitbull_HideBlizzard
Pitbull_LeaderIcon
Pitbull_PowerBar
Pitbull_RaidTargetIcon
Pitbull_RangeCheck