I just upgraded to 2.4.2 and everything seems to work perfectly, with one important exception: I can't save any pages/resources, even when logged in as the default admin user. When I try to save, I get the modal popup with the progress bar animation, but it never stops. If I right-click on an existing resource in the tree and try to publish/unpublish, duplicate, or delete, I get a popup error message: "Access Denied."
I can save everything else (plugins, snippets, chunks, templates, template variables) with no problems.
I've disabled all plugins, re-enabled them, and re-disabled them several times. I've cleared the cache several times. I've deleted the cache several times.
Anything else I should try?