The only thing that doesn't make since about the cause of the pop-up being provisioning is
AFAIK provisioning entails configuring the data login and SMS/MMS settings, so if that was problem data wouldn't work when the pop-up flashes up. Data works even when the pop-up appears saying that it doesn't. I can Google and run a sync with my Exchange server, just have to keep clicking the pop-up off the screen. The only common denominator about the pop-up is that it only appears when the roaming indicator (for us, the "Extended Network" banner) comes up. That's why my PRL fix works, because all I did is turned off the roaming indicator and no more pop-up. Some process or driver or something pops that message up whenever it thinks its roaming.
Now why some ROMs are effected and why the pop-up almost randomly quits happening between different ROM flashes beats the heck out of me!
I do want to ask if everyone can agree that the roaming indicator has got something to do with it. And please everyone that the pop-up has quit appearing for... give us the Custom ROM name and version, Windows Build version, PRL version, ERI version, and Radio version.