I recently got a copy of 3dsmax 2011 (up til now, I'd been using gmax). I can't seem to export. When I do, I get this error:
MAXScript Rollout Handler Exception

--Runtime error: FileStream cannot create: C:\Program Files\(blah blah my directory tree)\3ds Max 2011\scripts\nwmax\sanity\(model name)_sanitycheck.txt

I'm running 64 bit 3dsmax 2011 (student version) on an iMac with 64 bit Windows 7 (installed through boot camp). 16 GB ram with a quad core i7 processor.
I think I had downloaded the NWMax from this thread http://www.lucasforums.com/showthread.php?t=201912)
and I extracted the folder "NWmax" into the Scripts directory, and the autonwmax.ms file into the Startup directory.
When I start the "Autodesk 3ds Max 2011 64-bit" application, the NWMax toolbox opens fine, and I can import ascii.mdl files without problems. After making changes to the model, I select the AuroraBase and try to "Export Geom only" (I've tried with "Do Sanity Checks" both checked or unchecked), and then I get the error mentioned above.

When I used to use gmax, there was a separate NWMax startup application, which also launched gmax. Is there something like that for 3dsmax?

Rename your NWmax folder to nwmax...I know that sounds really stupid, but I believe the export script is looking for that specific path.

And no, there's no nwmax exe file for 3dsmax that I know of.

I gave it a try this morning, and it seemed to work. Thanks :D. I never would have thought, in a million years, that the folder name being case sensitive could cause a problem.

I'm having the same problems with 2010 and I tried that and it didn't work... :( any more ideas guys?

You get the exact same error message as redrob had?

Yeah, except that it is 3dsmax 2010 instead of 2011...

Another thing I discovered, is that with Windows 7, I ALWAYS have to right click and run as an Administrator. Otherwise, I can't export.