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