Well … sorta. I can’t upload any size of image, but previously I was limited to about 0.3MP (640×480). Now I can upload up to about 1.5MP without the dreaded Memory error. I can also use WordPress’s Auto Upgrade feature again.
Daddy Hogwash’s “WordPress 3.0 Upgrade Complete after Solving Fatal Error: Out of Memory Issue” is what fixed it. His suggested number of 40M fixed the auto upgrade problem, while I upped it to 64M to get larger images to work with my host, 1and1.com.
Update: There is no fix for this. Memory limit on my kind of hosting is ~34M. Any higher is not allowed. This seemed to work for a while, now doesn’t.
YARPP requires MySQL version 4.1 or later. Partly due to the age of my blog, I still had my WordPress database at 1&1 at MySQL 4.0. They now offer MySQL 5, and any new databases are created under the newer version. As I’ve used less than 5% of my database allocation, it was a simple job to create a new database, backup the old one, restore it to the new database, then point my wp-config.php to the new DB.
(If it still doesn’t work, view the source to your Settings→YARPP configuration page. Error messages are helpfully, if cryptically, embedded in HTML comments.)
I’ll probably still get a few “No Related Posts” appearing until the cache fills, but that should go away soon.