Version:            (using KDE KDE 3.5.2)
Installed from:    Ubuntu Packages
Compiler:           ubuntu dapper
OS:                Linux

Note this bug should not be confused with bug 129717 https://bugs.kde.org/show_bug.cgi?id=129717 where use of administration mode completely screws up my (and at least one other person's) xorg.conf file.  In the present case I stayed completely away from administration mode (once bitten, twice shy), but any attempt at changing the display power management interval resulted in the file
.kde/share/config/displayconfigrc being written with absolutely wrong height=350, width=640.  The result was the next time I logged into KDE, these wrong resolution values were used with ugly looking results.  The only workaround was to remove the above file before firing up KDE.  Of course my changed OffTime was not remembered in any case (see bug 128696, https://bugs.kde.org/show_bug.cgi?id=128696) so my whole use of displayconfig became rather futile.

What may be confusing displayconfig in my own case is I only use a single resolution.  This resolution is defined in the "Monitor" section of xorg.conf by 
 
 Modeline "916x687"    75    916  933 1066 1176    687  693  701  732 
 
 and deployed in the "Screen" section by 
 
         DefaultDepth    16 
         SubSection "Display" 
                 Depth           16 
                 Modes           "916x687" 
         EndSubSection 
 
This special configuration gives ideal results for the particular monitor I am using (and certainly much better than the 640x350 forced by displayconfig for my particular case!)

For now I have given up on displayconfig.  Instead, I use the tried and true display module which is part of Kubuntu dapper, but which is not displayed in any of the menus by default.  The way to remove displayconfig from the menus and replace with display is to edit /usr/share/applications/kde/display.desktop and /usr/share/applications/kde/displayconfig.desktop.  Remove the last line (NoDisplay=true) from display.desktop and insert it in displayconfig.desktop instead.