I've had the problem once to twice, and yes it usually involved having to import everything agian. If the problem is that chronic, then perhaps just imports your materials when you are ready to do the final save. Although it may seem like an odd suggestion, you can try switching WE's program emulation to windows 95 (done by right clicking on the .exe file---> properties--> compatability). That once solved a big problem I had with WE crashing when I imported stuff.
-VGsatomi