I run a number of different WP blogs, using different themes and formats. Since latest update of 2.9.1., I have not been able to create any posts when I have any Twitter related plug in active. I have had to deactivate all of them in order to be able to create any post.
I have installed WPhelpcenter on one of my domains (www.graemecodrington.com) and sent you my System Profile.
I hope you get this sorted soon as I need the link between WP and Twitter on most of my sites.
