This appears to be the same problem as unresolved topics 96665, 77207, and 112705. Commenters cannot register or log in nor can the admin login when using MSIE7. No problem with Firefox.
Using MSIE, If I try use login link on the sidebar of the main page, I’m directed to the login screen, and when I enter the ID and password, it simply clears and re-presents the login page. If I click on the comments link at the bottom of an entry, and then click on the “You must be logged in to post a comment” link, an attempted login takes me back to the original blog entry.
My blog does not have any underscores in the domain, does not use iframe, and does not use redirects or domain masking. I’m still running 2.0.5 on a GoDaddy Linux hosting account and am trying to decide whether to upgrade to 2.2.1, but the list of fixes does not include this problem. I like WordPress, but if MSIE users are essentially restricted to read-only, it may make more sense for me to use the time to migrate to a different package than to bother upgrading.
If this is a WordPress problem, is anyone working on it? If it’s not, can someone help me figure out what I’m doing wrong?