I\'ve given an ad hoc version of my app to some users. Two of them have the app die on start up while one user has no issues. I can also install the ad hoc without issue...but
Try using the iPhone Configuration Utility, a free download from Apple. I had the same problem, uninstalled and installed using the iPCU and now it works perfectly.
It's somewhat unintuitive to use, try googling for provisioning profile iCPU. I found detailed instructions on a "redfin's developper blog".