Shoppers cannot update address - only Admins?

[lily64]

Strange issue and I cannot find a setting or anything anywhere for this. In the cart, the only people who can update their billing and shipping information (address) are admins. Registered shoppers cannot - I get a 403 error. Any idea why this would be and where to look to resolve it?  Thanks for any assistance.

[jenkinhill]

Start here: http://forum.virtuemart.net/index.php?topic=79799.0