Help! ?Itemid=143 is being appended to all VM URLS and causing problems!

[Artificia]

Please can someone help? Something very strange is happening. I am finding that "?Itemid=143" is being appended to all the URLS in the VM2 shop.

We have Joomla 2.5.14 and Virtuemart 2.0.24c

This is the site, which is now live but is causing a major problem because the check out isn't working properly:
http://geetac.co.uk

I find that if I remove the ?Itemid=143 from the end of the Cart page, it then does the job of calculating shipping rates and displaying shopping cart products as it should. But otherwise, the shipping calculator doesnt work and the cart does not list all the products that have been added to the cart.

Please help! This is very urgent!

Thank you

Caroline