After installing TomTom navigator 7.916 on Windows Mobile I soft reset the phone and I get an error saying " BTTrayCE is not valid pocket pc application".
Rename these 2 files in your windows directory on phone:
BtCoreIf.dll
BtSdkCE30.dll
(for example: "BtCoreIf.old" "BtSdkCE30.old")
then reset, it will fix them.