If you find you're getting dumped out of Quake 4 (or any Doom 3 powered game for that matter) during a gaming or editing session without any warnings or errors pooping up, then add the following to your desktop shortcut to 'force' the game to write what it's doing when it starts up and crashes out to a text file so you can at least see what the last thing it was trying to do before it crashed out;
+condump log.txt
You should end up with a short cut that looks similar to the following (assuming you don't have any other command variables in place);
"C:\\Program Files\Quake4\Quake4.exe" +condump log.txt
Adding the above will save a text file to the root folder of your game install, usually where the game *.exe resides. You can then open that into Notepad or similar text editor and read through the files to see exactly what the last thing the game did before it crashed out
