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