That is a weird problem, particularly that it happens on only one of two macs you have.  It certainly doesn’t happen for me.  If I open Chimera’s IDLE shell and type in similar commands to yours, they work fine.  If I run the commands from a file (attached), they also work fine.  So you should probably look at the saveSession() routine in SimpleSession/save.py and (on the problematic mac) make the same calls as it does and see what they return, namely:

what does os.path.dirname(“current_session.py”) return?

after your os.chdir(path), what does os.getcwd() return?

what does os.path.exists(path) return?

If those look okay, you probably should insert print statements in the saveSession() routine to get some kind of idea about what’s happening.

—Eric