After an upgrade to 1.4.1 I don't receive an email when someone posts something in my forums. The cron-job seems to work correctly. Are there made changes in the way Moodle handles email?
From your two problems I'm guessing you have some database corruption ... go into phpmyadmin or the the Moodle MySQL admin module and REPAIR the tables. You need to click on the database name in the left frame, then select all the tables and select repair from the menu at the bottom of the right frame.
I repaired the database... No resultst 
Did you visit the admin page directly after upgrading the files, to let Moodle upgrade the database properly?
Unfortunately I didn't make the Internet site inaccessible before the upgrade. During the first minutes of the upgrade I myself visited the site and saw that the database adaptation started already. Immediately afterwards I blocked the site, but to late...?
On this topic, is there an exhaustive list anywhere of support for e-mail notifications. (e.g. which modules and which events can be notified using Moodle e-mail alerts or digests).
It would certainly be useful to demonstrate e-mail notifications to the prospective users of my Moodle installation to encourage them to use it as a point of coordination (e.g. notifying students of new assignments and teachers of new submissions would be v. useful).
However I don't know what range of events can trigger an e-mail notification. I suspect from recent posts that the assignments example specifically does not support e-mail, but I'm still a bit in the dark as to what does include e-mail support.
It would certainly be useful to demonstrate e-mail notifications to the prospective users of my Moodle installation to encourage them to use it as a point of coordination (e.g. notifying students of new assignments and teachers of new submissions would be v. useful).
However I don't know what range of events can trigger an e-mail notification. I suspect from recent posts that the assignments example specifically does not support e-mail, but I'm still a bit in the dark as to what does include e-mail support.