Jun 052010
What does the Update PRL and Update Profile do under the System Updates option on the HTC Hero?
The PRL is called the Preferred Roaming List. It is a file in your phone that has a list of all roaming providers Sprint works with. When a phone cannot find a Sprint signal, it checks the PRL for the first available provider.
Update Profile: This will refresh your data service parameters such as username and password and help clear out any memory issues that might be affecting the device.
Via: http://community.htc.com/na/htc-forums/android/f/17/p/1984/6619.aspx