I was able to solve the problem of the submission form not redirecting to another thank you page. My page footer was missing a call to wp_footer() (or something like that) – that was supposedly required to make the JS work. So, for now, my tracking works well by redirecting to another page. However, I would still like to know if there is a way to track conversion without redirecting to another page.
In my case it turned out that call to wp_footer was missing in the footer – that fixed my issue.
I have the same problem. It worked fine from April ’11 to until recently – it has suddenly stopped working and I haven’t made any website changes! I want to track Google Adwords conversion – is there an alternative to tracking it without re-directing to another page?