Doom builder Error: Saving map fails every so often

I have out up with this for ages now, and it's beginning to drive me to madness. Anyway, this happens every so often, not every time.

Error 5 whilst saving map: Invalid Precedure call or argument.

I dont know if it happens to everyone or not. The only way I have found to fix it is to load up filename.wad.backup1, and save it as something else.

Could somebody let me know if there is a way to fix it.


Thanks