Fundraiser pledges not being recognised

I have set u a fundraiser on my site but when a pledge is made the return page says the pledge has not been found and try refreshing, but this makes no difference.

I also manually added a pledge which is not showing up on the pledge info in the widget or shortcode.

The site uses WP Supercache, would this be the problem?

the IPN is set up as described in the Fundraiser docs.