You can try interlace modelines, but the interlace feature in the 4xxx drivers and maybe earlier is broken. Hopefully this will be addressed in the next release.
For more info to help you with online modeline generators, I believe you can search for a document floating around on the web called "Xfree video timings howto" (?). If that's not the title it's something close. That will define some terminology for you.
Pixel rate, I believe, is just how many pixels your card can pop out on the screen per second. You can specify a value for this in a modeline as long as it is within a valid range (Xfree86 log has info on this). My experience is that most nvidia cards' range is something close to 12MHz up to 350MHz. That's 12 million - 350 million pixels output per second.
I think people use pixel rate, pixel clock, and dot clock interchangeably.
If you see leibold's last post his pixel clock is 10.09. I don't think that will be within the valid range. I would expect for startx to fail, and that you'd be able to see errors in your XFree86 log file complaining that the pixel clock is wrong.
Hope that helps some, and I hope the interlace feature in the Nvidia linux drivers gets fixed. The feature might not be as important as it used to be, but it is still useful to many people.