Monitor "out of range", can some one help?

For my G4, I have purchased an Envison monintor. I went to set up the monitor and change the resolution in the "Diplays." Apparently, I have chosen a resoultion that seems either too high for the monitor or the monitor does not support that resolution. I receive the prompt "out of range" on the monitor and I am unable to return to the desktop in order to change the resolution to a lower one.

Has this happened to anyone and if so, how do I change the resolution back?

Thanks,
Wes