I had this same problem with my HD7850 & Philips 27" Monitor in Linuxmint 14 KDE (as well as other ubuntu 12.10 distros).
However my fix may be SIMPLER
I changed my default refresh rate to 50 HZ (originally was 60HZ), then I changed my overscan/underscan setting to '0%' and rebooted.
Surprisingly this saved my settings and my rebooted machine looked perfect!
For a while I kept my refresh rate at 50HZ, but today I decided to change back to '60Hz preferred' and VOILA, I rebooted and my overscan/underscan settings were still saved.
I hope this helps and works for everyone else
To do this in Linuxmint 14 KDE:
- click on the 'kickoff application launcher' menu (bottom left hand corner for me)
- type 'amd' into the search bar
- click on and launch the 'AMD Catalyst Control Centre (administrative)'
- enter in your password if/when it asks
- select 'display manager'
- then find where you can change your 'refresh rate'. Mine defaulted at '60Hz preferred'.
- change this value to 50 Hz
- then under 'display manager' click on the little box with the plus sign in it.
- the click on 'DTV (1)'
- then on the right hand side under the 'adjustments tab', you can change your underscan/overscan options.
- change to the desired values (mine was 0%)
- apply these values and reboot.
- then open and launch the AMD Catalyst Control Centre again and simply change your refresh rate back to 60HZ.
- reboot and fingers crossed your overscan/underscan settings are still saved