I am using solidworks for a year almost and i just got this problem and i have no idea why it is happening since i did nothing wrong... ANyway i have drag and drop failed error. It happens when i create an assembly that has flanges and insert it into new assembly. So as long i have no flanges in my top level assembly i am able to get drag and drop. But if my assembly has sub-assemblies with the flanges, drag and drop fails. It also fails even if i have some of the subassemblie opened in the back, but not inserted into top level assembly yet..it also will not allow me to open the library part...

What am i doing wrong here....?