Thanks for the feedback. I hadn't considered disabling Gears. Today's a new day, though -- here's what happened:
I walked away from by blog for a day or so, then got back into it today. When I went to the dashboard, suddenly the newsie items at the bottom that had been giving me some kind of "fetching data" error, suddenly had content. OK.
So I went into a post and tried to add a category. The new category box popped open! When I typed in a new category and hit save, I got the error message:
Warning: Cannot modify header information - headers already sent by (output started at /Users/gregraven/quotes/wp-config.php:153) in /Users/gregraven/quotes/wp-includes/classes.php on line 1586
So I went to wp-config.php and checked line 153. This line and the line above it were blank, so I deleted them. With no other changes, my blog started working right.
So I checked the pages to see that the formating and content were OK. The new version had added a couple of things back I didn't want, so I tried to edit them out in the built-in editor. No save button. Hmmm. Well, I used Fetch and BBEdit and made the fixes.
Bottom line, there are still some bugs lurking about -- perhaps in Gears -- but at least my blog is working again.
Thanks again for your help.