Adding products to cart and cart deletions

[GetResultz]

Guys,

my web designer has just put my web site live and it's based on Joomla (1.7.5). She also installed VM 2.0.2 but neither of us have any idea about the following issues:

It seems to be a common problem that IE versions up to 9 and older Firefox and Chrome versions have a problem with 'Add to cart'. Thats the first issue.

The second one:

Regardless which browser and system I use (I have a Windows based desktop PC and a MacBook pro) and use the following browsers: Firefox, Chrome, IE 9 (on the desktop PC) and Safari on my MacBook pro. Both systems etc. have the latest updates installed.

So, when I add two products all is fine and it adds up etc. However as soon as I add a third one, the cart gets deleted and nothing is in the cart any more.

I am an absolute newbee and I read something about jQuery etc. but please, please help me to solve this issue!

My website is www.GetResultz.com.au and then navigate to 'Shop'


I greatly appreciate your help and support

Cheers
Patrick