It's a little annoying to see such posts.
First off, you made no mention anywhere of whether your board was vanilla phpBB2 or a MODed one (slightly, or heavily).
No mention of what software you are using on the server, PHP, MySQL (or whatever pther support DBMS), webserver (IIS/Apache/etc).....
As there was only one issue that popped up in 2.0.1 that broke in comparision to 2.0.0, and that only affected those that were upgrading from phpBB1.x anyway.... the problems you are seeing could be a combination of:
- Partially updated files, eg: /includes wasn't updated, yet / was.....
- You have a "quirky" server set-up.
- You run a MODed board, but didn't apply said MODs to the new files..... If you ran the patch file from CLI (which I assume you didn't.... since there's no mention of it) the hunk errors that were reported weren't resolved
- Your host changed server config, disabled SMTP/sendmail etc....
... and the list could go on.
If your errors were genuine errors, then it would also be a lot more helpful to everyone else (developers and users) if a detailed bug report was submitted so that it can be fixed for the next service release.
As for 2.0.0 not having any issues... This list is obviously a figment of my imagination.... -> http://www.phpbb.com/phpBB/docs/README.html#200