I have been working in Inventor 2014 with a large assembly approx. 800 number of parts and 30 number of subassemblies and 3 different Levels of Detail. I have been trying to export the Master level of detail as a STEP file. Everytime I attempt to export the file Inventor does not respond and then crashes. I have no problem working inside the assembly. I was able to go through and fix all constraint errors that i had thinking that was the problem, but it still crashes when I go to export the file. I tried exporting a smaller assembly to a STEP file and I was easily able to export that file, is there any limitation to the size of assembly when exporting?
Is everthing in one folder (if not Pack and GO to a folder). How large is the total assembly?
What are the specs of your machine (RAM, free HDD)?
This can happen if the installation of Inventor wasn't done as the Local Administrator of the system. One way to address this is to log in as the Local Administrator of that system Inventor is installed on and then open Inventor and try exporting a STEP file. If you can then log out and try logging back in as a user and open Inventor and try export a STEP file angain. It should work. If not post the results.