Wow 4.0 introduced a feature to hide enemy debuffs cast by other players on the built-in target frame. By default this option hides most of the debuffs cast by your raid members on a boss, which some players find annoying. A recent wow patch broke the configuration option that disables this questionable feature, so now those debuffs are always hidden unless you manually reset the configuration option every session.
This tiny addon fixes the bug in the configuration options so that it properly respects the user's setting and preserves it between sessions.
Mists of Pandaria Info: Starting in WoW 5.x, this bug has been fixed. Therefore as of 5.x this addon is officially end-of-life.