Fundraising: add backslash before pledge

I cannot get the Fundraising plugin to work on a single site installation. I've tried it with two different hosting accounts with the same results.

However, it works on a multisite.

I've set up a fundraiser and when the "support this project" button is selected, it is redirected to http://sitename.com/fundraisers/funraisernamepledge/

instead of: http://sitename.com/fundraisers/funraisername/pledge/

Can someone shed some light on this?