Running Dominos 5.3.1 and my possess bar is failing to show up during the last battle of Drak'Theron Keep. Another computer in the house is running the same version and it is working. I tried switching profiles before the fight and same problem. Everything is default settings except I've turned off use blizzard override action bar, and I have arranged the bars.

Well, this is going to be fun to debug :) Now for a ton of questions:

Are both players using the same class? If not, then I'd try swapping computers and see what happens.

Are both computers running the same set of addons, along with the same versions of each? If not, then it could be an addon conflict. For this I'd try running with just Dominos enabled.

Are both computers running the same OS? (Again, this shouldn't have any effect, but its something to look into)

Seems related to "it looks like they have implemented [shapeshift] for temporary shapeshift scenarios like the last boss in Draktharon Keep"
Source: http://www.wowinterface.com/forums/showpost.php?p=283282&postcount=15

I've adjusted the override controller bit of Dominos to use the new macro conditional