I was getting the same problem (vue 4 pro crashing in XP when using the material editor) The latest patch (4.52 for pro) fixed that for me but I still get it every once in a while on my laptop in Vue D'Esprit 4. If you don't have the latest patch you might try that, just my two cents.

If this is Vue Pro, it will prompt you to update the file (which will re-import the object) and if you say "yes" to update, it will then prompt you on whether or not you want to update the textures that are currently applied to the model (but only if you have changed them in vue.) This also applies to other file formats as well, as long as the file you edit in the other program has the same name and location as what you have imported into Vue 4 Pro. Hope this is what you were looking for.

When I've needed to do a signature and don't want to bother with post processing it in I have created one by using the terrain editor (similar to the method of bringing in DEM files through the editor, create a terrain, reset it and click on "picture" and load an image of any text created in windows paint or any paint program and then adjust accordingly, it tends to look bumpy just because of the nature of terrain objects but it works and I'm sure you could smooth it out if you were so inclined. Then just apply any material you want to it and increase the "luminous" effect in the effects tab of the mat. editor and you're all set (just be sure to turn off "cast shadows" as well) This may seem like a lot of work but you only have to do it once and save it as a vob object for future use.

I also have that problem with XP and the material editor shutting down Vue 4 Pro without warning as well. Occasionally I actually do get a "microsoft has encountered..." error but for the most part it just boots me out of the program. It didn't seem to happen to me until I got a new machine (an HP) that had hyperthreading (multiple processors) enabled on it. Not sure what to do about it except to save often before doing materials. If anyone has a better solution to this irritating problem I'm sure it would be helpful to those of us having this problem. Thanks.