Hello,
I just update my solidworks 2013 to 2015 version and I realized that my assemblies files got many problems because they have lost references that are bounded to other part of the same assembly. Here the example:

- I have an assembly and I insert in it a Part A

- I create inside the same assembly a Part B, designed around the Part A. I created planes and sketches in reference with the Part A

- everything worked just fine in solidworks 2013

- I updated to SLDW 2015 and this relation are gone

- I try to fix the problem rebuilding the relation manually but Solidworks tells me that I can't create relations with another part

- my old files have to be trashed (!!)

Is there anyone that could help me to find out the problem before I switch to Inventor?