My site is http://www.darrengibson.org . Everything was fine with my installation until I upgraded to 2.6.1. Now, everything "front end" wise is fine (content is available, categories are browsable, etc.), but when I attempt to access http://www.darrengibson.org/wp-admin (or /wpadmin/index.php or /wpadmin/upgrade.php etc.) I get a 404 error.
I have verified that the folder and its contents exist on my server, and have re-uploaded a few times. I worked through a few similar posts here with no luck. I cleared my browser's cookie cache. I even downgraded back to 2.5.1 with no change. I'm now back to 2.6.1 and in the same boat--the "read" functions work just fine, but I can't log in to the admin panel. Does anyone have any ideas as to what might be the issue?