The Modeler specifically needs the Microsoft .NET Framework version 3.5 SP1. It was never tested with (and probably won't work with) .NET 4.0.
For a download link, see this page.
We've used XP here extensively with the modeler and never experienced any problems. Here's a quick troubleshooting guide that might help you out:
(ps: it's easiest if you edit your original answer to reflect any additional information you acquire. That makes it easier for other people who find this thread to determine whether the answer provided here could help them. Thanks in advance :))
Thanks,
That was indeed the issue. Modeler works now. (although I had to uninstall all my installed previous .NET versions, and manually install all eleven .NET versions and patches for the 3.5sp1 .NET installation to work)
Kind regards,
Jan
To give some more information: Mendix 2.4.6.2 does install and run correctly. However, Mendix 2.5.0 and 2.5.0.1 both crash if i try to run it after (a seemingly successful) installation. No error message, just a "sorry for the inconvenience" crash. I have the latest Java JDK and .net. (Java jdk1.6.0_21 and dot net framework version 4).
We also tried installing 2.5.0.1 on another machine (with the same java JDK and .NET versions). Same problem. Here it does give an error message in the crash: "Modeler.exe - .NET Framework Initialization Error: Unable to find a version of the runtime to run this application."