Just to let you know,

I went the hard way and restore form by backup piece by piece. I finally found 7 .scx in my forms directory causing the problem. These where old forms which I did touch for weeks. I suspect Norton antivirus to have cause the problem because it lunch automatically every monday morning... I might have tried to rebuild while norton was still running, I'm not sure.

Thanks for your help, it point me where to look for.