I could not understand how RIM could possibly be so clumsy to break DM5 with OS5. Therefore it MUST me something I installed and not RIM - So I simply deleted applications, one by one, until I found the one that broke DM5.
SmrtGuard is a paid-for application. It uses email to communicate with it's own servers and to make things happen on your device. (A special email, for example, will make your device scream for 10 minutes - very helpful if you can't find it in your house