Not an easy question to answer without more information, Keith.
How large are the assemblies in question? What are your system specs? When you run SolidWorks Rx, do you get any warnings? While it should really matter, are you working locally or across a network?
The asseblies are 460KB. I'm using Solidworks 2012 X64 with SP5.0 on a network.no warnings just stops working. Seems to be running just freezes up, seems like there is somthing going on in the background.
I'm going to guess, from what you've said, that it's your graphics card. Run SolidWorks Rx (Start->All Programs->SolidWorks->SolidWorks Tools) to find out for sure.
460kb is a tiny assembly, are you sure that you don't mean 460MB? Also, how much RAM do you have?
I don't know.... You have not given us much info to go on.
What version and service pack of Solidworks?
Student or Commericial license?
What are the specs of you computer?
Video card and driver? Are they on the approved list for SolidWorks? http://www.solidworks.com/sw/videocardtesting.html
How big or small is the assembly you are working on?
What type of parts are in your assembly? Imported parts, surfaced parts, or......