Similar to PHP Session info and Marketpress' "Whoops. Looks like you've missed a step

I have exactly the same problem (Get the message: Whoops. Looks like you've missed a step), but in my case I switch themes (to Twenty Ten 1.2 ) and everything works fine. I see sometimes the page bounces (a quick reload) when it loads for the first time (Cache deleted). What exactly should I look for in the code? What tool can I use to follow up this? Any suggestions?

Also when I check the orders I receive the information before the header page, and also where it should be (Twice). But this problem also disappears when I switch themes.

When I switch themes I keep all my plugins on. Which are:
advertwhirl/Advertwhirl.php
events-manager-extended/events-manager.php
greybox-integrator/greybox-integrator.php
marketpress/marketpress.php
really-simple-facebook-twitter-share-buttons/really-simple-facebook-twitter-share-buttons.php
salesforce-wordpress-to-lead/salesforce.php
swfobj/swfobj.php
wp-polls/wp-polls.php
wpmudev-updates/update-notifications.php
wptouch-pro/wptouch-pro.php

I hope you can help me guys I find your plugin great

Regards