I don't really believe that this is a problem with 2.3 RC1 but I have to check here first before I go after my host.
Has anyone else that's using WP 2.3 RC1 having a problem with posting a comment and the page not refreshing (logged out) with email notification turned on?. I found that the send mail process was hanging on the server side which allowed the comment to post but the page to hang in the middle of refreshing. This causes a blank page in Firefox and a "Cannot display this page" (whatever) in IE.
This happened once before with 2.2 but it cleared up after a couple of days. This is just a "just to say I did" type of question here before I call my host. It might just clear up like last time but I'd sure like to know what might cause this to happen.