Do a /powa debug, are there any error messages? Ones that can be safely ignored are the load time messages, and anything dealing with GetScreenEdgeDistance.
If there's anything else of note, click the copy button on that particular row (the page icon) and paste it here.
If there isn't, could you upload your saved variables somewhere (WTF\Account\<Account Name>\SavedVariables\PowerAuras.lua, can open it in notepad and paste the text onto
Pastebin)?
Also one other thing, are you using RC 1 or RC 2? RC 1 had a bug with Unit Power/Health triggers that was fixed in #2. The easy way to spot the difference is that help text won't be present on the Support Triggers category on RC 1.