This is probably a dumb question and probably has a simple answer. I haven't been able to find a solution or figure it out yet though. I have experienced this multiple times over the last few months, so its probably something I am doing wrong.
For example, I have two documents. When I try to paste an object from one document to the other, after the object is pasted, the document will continue to freeze off and on with the spinning beachball (OS X). I am almost positive this has something to do with the materials because when I remove all the materials from the object first and then copy and paste it, I get no freeze ups at all. I guess I am just wondering what is causing this, because it happens with complex and even very simple objects... but only if they have materials on them.