Instead of using Configure My Desktop, use the PCC (configure my computer)
Press PCC button > enter admin password > click on Hardware > Configure your Video Card.
Under Monitor, you will probably have a suggested type (mine says hp L1702)
With Resolution click on the value showing which will produce a drop down menu - you might have to go for Other to find your desired resolution. After accepting the new setting, and Quit, leaving PCC, you will need to log out. No need to reboot - just log out will do. When you log back in again, your new setting should have taken effect and, more importantly, will persist from then on. This resolution here is 1280 X 1024 and it is locked in. With the laptop however, I use 1366 X 768