AutoCAD file refuses to open - stuck at 93%

I have had a terrible time with a group of dwg files that would not open. No matter what I did, they would not open (always stopping at 93% open). We create 2D dwg files from NX6 drafting files and have really not had any issues until yesterday. I tried opening the files in AutoCAD 2010, AutoCAD 2009, tried inserting like blocks, tried Recover, tried drag and drop. Nothing helped. Funny thing, I can open them quickly and smoothly in Dassault's DraftSight software (free by the way). Then I had an epiphany; I opened them in DraftSight and then removed the customer part file (a complex casting drawing made mostly of splines). Saved the file and what do you know, AutoCAD opened it up with no issue. Hmmm, I guess Autodesk could take a few pointers here and figure out how to open up dwg files better. I am back in business