Hi Mike, it's not unusual for it to take a while to load STEP files, 3 minutes is not nearly enough time to wait.

Also sometimes the size of the file on disk can be deceiving, if the file contains a large number of repeated instances that can balloon up the complexity at runtime by a lot.

If the file is heavier it's not a bad idea to change some of the view settings in MoI so that it will be generating a coarser display mesh instead of the default dense mesh, there is some information on that here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5322.2

Coarser view settings will help to consume less memory and take less time generating the display meshes if there are any complex surfaces in the STEP file.

Also right now when MoI is busy loading any file the UI will appear frozen while it is crunching away on the file. If MoI is still using CPU in task manager it means it's still working and is not actually frozen. I am planning on tuning this up in v3 so that it will show a progress bar or something during the load instead of just looking frozen but right now that's just how it works.

- Michael