[RodMyers]

just upgrade to 1.29.0, and now will not start. 1.28.* did, as of yesterday

From the command line I get this error;

calibre
Traceback (most recent call last):
File "site.py", line 58, in main
File "site-packages/calibre/gui2/main.py", line 452, in main
File "site-packages/calibre/gui2/main.py", line 320, in run_gui
File "site-packages/calibre/gui2/ui.py", line 26, in <module>
File "site-packages/calibre/db/legacy.py", line 19, in <module>
File "site-packages/calibre/db/cache.py", line 18, in <module>
File "site-packages/calibre/customize/ui.py", line 15, in <module>
File "site-packages/calibre/customize/builtins.py", line 654, in <module>
ValueError: bad marshal data (string ref out of range)

I've attempted to remove the calibre folder, to see if any of the plugins were the problem.

Same error