The same thing happened to me when I was first learning my 396XT. I didn't now how I enabled it and It took me a while to figure out how to turn it off.
The 396XT has a "search with scan" mode/option for each 'service'. It's actually a nice feature, but can be irritating if you enable it by accident. To disable it:
1. Note which 'service' (or services) is enabled when in scan mode.
2. Press 'menu'
3. Scroll down and select "search for..."
4. Select "Edit Service"
5. Select the 'service' you wish to disable.
6. Select "Set Lockout" and change the status to "Lockout".
..and that's it. Happy Scanning.
