UPDATE: On some systems (mine) the DTM mod does not like the rfdynhud d3d9.dll file that you have to install in your rFactor folder. I removed that file and the rfdynhud plugin completely and the problem is solved.

Great news Dirt Diver, I'm really pleased you got to the bottom of it. I know disabling rfdynhud isn't an ideal long term solution but at least you now know what the problem is.

I stopped using it a while ago becuase it caused me no end of grief with runtime errors and lockups. I went back to the trusty XD which i've used since the GTR2 days and never lets me down. Doesn't have nearly as much info as rfdynhud or some of the others but i like it and it just works.

http://www.vitumo.de/

You may want to try this -- or not. I am running it on my i7, Win7 64-bit laptop and it seems to help.

Disclaimer: The file I downloaded was clean, but scan it thoroughly before opening the file.
Make sure you backup your exe file. If it turns you computer into a radish, or screws-up rFactor, don't yell at me.

http://www.ntcore.com/4gb_patch.php

Was Jon C running dynHUD? Perhaps that's just compounding his problem.

I was using XD which also uses a d3d9.dll overlay. I've removed that now and I've installed the latest Direct X (thanks Doug). I'll see if I can make a few tweaks to my plr - maybe reducing opponent detail will have an effect. I'll give the DTM mod one more shot - if I get time I'll do some tests on my own server.

Jon

I propose that this thread gets stuck, in order for easy access. All this info is very valuable.

Seconded...