I've been having this problem recently. I have an assembly, and let's say that I've just done a simple operation like create a new mate. If I click save, the file suddenly increases in size significantly, like on the order of several megs. Some (even simple ones with only a few components) assemblies of mine that started out small have now gotten so big that SW now takes a long time to load them or perform any new operation. I have started experimenting to try and figure out what the problem is and I have now found out that if I click save after not doing anything to the assembly, the file size still keeps increasing, many times still several megs with each and every click of save. This seems to have started after I installed SP 2.1 on SW2010 x64. Does anyone else have this problem or know WTF is going on?