My sketchUp model crashed when attempting to use Clothworks. When I re-opened it, it had become a “Read-Only” file, and it was Locked. How can I undo the “Locked” state?
you might consider opening it and simply saving it as.
if not,
select the file, press cmd-i and in that panel, check at the bottom to see if you can give yourself writing rights.
files get locked while sketchup write in them. if it crashed before the end, it might just be that.
but I would really start by doing the save as thing.
I would do the Save as … thing as @ateliernab suggested but then I would do a cold reboot of the computer, reopen SketchUp and the original version of the file to see if it is still shown as locked.
Thanks to ateliernab and DaveR. I did a save-as and it works fine. Very annoying the crash due to Clothworks no longer being compatible with my system, and then losing all work that day (no autosave, complete loss of all work since last opening.) But appreciate the ability to recover at least an earlier version of the model and rebuild.
S.
no longer? it hasn’t really been updated in years, where did you see that info ? 
if that’s the case, copy the elements that should work with clothworks in a different file. and do the simulation there. if it works, copy the result to your project. if it doesn’t you’ll only loose the extra file.