Late to the party, sorry folks...
As Nick stated - I've run into issues with 3.65 b7173 and the SIM file format, especially since moving to Windows 10 (firm choice, not mine). I also don?t have a magic bullet....when this starts happening I try the 'easy' stuff of moving the project's working directory; then moving the directory & having another modeler run the model on their machine; and shut down & restart.....mix & match the above.
Then I go to the next level of removing, installing & reinstalling, either 3.65b7163 or b7173 .....rinse/lather/repeat ...as needed....this is both time consuming and a bummer as we have several elements that we add back in.....which go away with the reinstall steps....

In summary....1) hope it never happens 2)start with the easy steps of moving the project files around 3)remove/reinstall

Thanks,
DARIC R. ADAIR PE, C.E.M.
Henderson Engineers, Inc.?|?Mechanical Engineer, Energy Analyst
DIR 913 742 5530? TEL 913 742 5000? FAX 913 742 5001? TX ID #F-001236? EMAIL daric.adair at hei-eng.com? www.hei-eng.com
Licensed in KS.?