Yeah, WMM used to always crash on me as well. It has issues with codecs as well with memory. Mine kept crashing as well which is why I didn't even try to use it but disabling the ffdshow (or other ones I've heard) seems to have fixed it. What you do is go to Tools->Options and then go to the Compatibility tab and you can turn off ffdshow or other codecs until it stops crashing on you. Other helpful sites to check out too are: http://www.papajohn.org/ (go to problem solving on the left) and WMM2 forums here: http://www.windowsmoviemakers.net/. Both have helped me out.

I really hope that it works for you and you start vidding again. It's a lot of fun and I'd love to see vids from you :)