A few days back, Jeff had told you about WordPress 2.9.1 being around the corner. The WordPress team has worked hard to get it out of the doors and a beta version of WordPress 2.9.1 is now available for downloads. It fixes bugs with scheduled posts and pingbacks which some users had been facing, due to a bug in curl.
The new version is not immediately available for downloads through the automatic upgrade, however you can download the WordPress Beta tester plugin and go to Tools->Upgrade and perform an automatic upgrade.
Please remember that this is not the final WordPress 2.9.1 release, so you might want to wait for another day or two for a stable release, if you are not comfortable using beta versions.