When my previous display started getting fuzzy, I plugged in another display and got a much clearer view until I rebooted. After the reboot, the display came up as 1280 x 1024 resolution instead of my usual 1600 x 1200. I went searching and found references to capturing the EDID from the display and correcting the EDID information. Using the Nvidia X Server Settings applet I captured the EDID, but the Phoenix editor was unable to open the file. In researching further, I was looking in the X-Server logs, and the binary data in the capture was the same as what I saw in the log file, so that at least checked out, and I have no idea why Phoenix can not open the file.

However, there is usually another method to the same destination. I plugged in my previous display and captured the EDID information from that display. Then I specified it in the "Screen" section of my xorg.conf file, snippet as follows:

Section "Screen"
Option "CustomEDID" "CRT-1:/etc/X11/edid-nokia_445za.dat"
EndSection

Note: I learned the correct device name from the X-Server log, in my case it was "CRT-1".

Upon reboot now, the clearer monitor comes up with 1600 x 1200 @ 85Hz refresh. Success!

I think this should also work for computers attached to a KVM switch, where the display adapter is unable to query the monitor with the KVM switch connected in between.