It happened again - (first time about 2 months ago)
Open a drawing when you don't have all the parts referenced in the drawing already opened and (sometimes) solidworks will lock up.
Files open at the time become corrupt and will never open again, including backup files (in the swbackup folder)
Longer: I designed a family tool today with 5 seperate parts. Finished the mold assembly this afternoon. Started the drawing. Decided to open another sw drawing to reference some information - the above error occurs - forcing me to kill task and restart sw. Try to open my family tool part (sldprt file around 50mb in size) and sw gives an 'error opening document' message and then crashes....
Guess what I'm doing tonight.