Initially this sounds like a hosting problem and not a WordPress issue. Where are you hosted? Shared? Dedicated? php version? mysql version?
Run through a typical wp hack protocol and check for base64 code in wp-config.php, any theme files and akismet plugin files… also any other php files. Database hacks are sometimes hard to find too but mostly located in the wp_options table..
Read into the hack fixing at Dre’s site: http://blog.sucuri.net/2010/07/understanding-and-cleaning-the-pharma-hack-on-wordpress.html
TODOS:
Turn off ALL plugins
Check in settings > writing in the “update services” section… for now just make sure only rpc.pingomatic one is in there remove the rest.
Check in settings > Discussion and for now uncheck “Attempt to notify any blogs linked to from the article”…
Try to post…
what happened?
— hopefully one of those fixed it. I’d also try the above but try a fresh install of the twenty-ten theme and change your site to that theme after fresh install and try posting again.. could be something in your theme…
LMK