Add to cart showing 'page not found'

Hi,
For some reason whenever you click the add to cart button on any of my products it displays the 'page not found' page instead to the cart page.
I am not sure why this has started happening, however I did attempt to install Ultimate SEO Urls approx a week ago, however upon discovering if was no use for me I thought I deleted all the files. This may have something to do with it, unless its related to another issue?

You can see for yourself by click 'add to cart' at my page:
http://calluccimenswear.com.au/index.php?main_page=product_info&cPath=2&products_id=4

Thanks in advanced!

The add to cart appears to be working on the site you listed. There was a bug present in "Ultimate SEOs" when using the option "Categories as Directories". The information on fixing this bug are listed in the Support Thread for Ultimate SEO URLs.

If you get a chance, please try updating your .htaccess file and let us know in the official support thread if it worked in your environment. If after making the listed changes you are still having issues please let us know in the Support Thread for Ultimate SEO URLs.