I'm experiencing some big problems...but before I start...if you tell me to "search", I will hunt you down, forcibly migrate your site to a 386 running Linux off a 2400-baud modem, and then taunt you mercilessly. :) I've searched here, I've gone through Google, etc.
Here's some info: PHP 4.3.9, Apache 1.3.33, MySQL 4.0.22, Linux (2.4 kernel)
(so here's a hint - don't try to give me the IIS-specific fix - I even tried it for kicks and grins!)
For a while, I'd been having problems with redirects not working under 1.2. I'd approve a comment in moderation, and it would just say "wordpress 1.2, 0.02 seconds". If I directly entered a page address, it would work fine.
So, I decided to do the upgrade to 1.2.1. Actually, given my DB had cruft in it dating back to b2 0.6, I did a fresh install into /wordpress (existing was in /blog), installed into a fresh DB, then migrated my tables over. Everything was running good, so I decided to make the swap. I updated the WP directory and blog address to /blog/, and did the folder renaming.
Next time I clicked the login button from my blog, it gave me the login dialog. I re-enter my username and password, I get the "ERROR: The password field is blank" error message. It doesn't set login cookies. (it's not a security issue - I have gallery2 on the same domain, and it can set a login cookie).
So, I've got a useless site right now. I'm going to see if I can hack together a bypass script that will manually set my login cookies, but there's still something messed up here.