I discovered something odd after updating.
If I go into the installed plugins page and deactivate a plugin, that works fine. However, if I click on the "Delete" link, nothing happens. If, however, I check the box in front of the plugin listing and then use the bulk actions box and select delete, that works.
I've also noticed a couple of plugin settings pages where some links work and some don't, but don't know if it is related.
Fortunately, there is nothing that disables my site, but if anyone has any ideas, I'd appreciate hearing.