Hi Piszi, Please provide website url. VM 2.0.8b we are testing right now.
Hello it is uploaded to haztartasi.netkereskedes.hu but right now I modedd it a little bit

Mods:
Shipping, Payment and discount update completely disabled in the JS.
Changed ordering, and now product list is first and billto second
added a jquery clone function to email and first name so right now email value is cloned to username and last name to diplayed name
disabled browser auto fill and copy paste because of the clone
I hid the username, and displayed name by making them block with css
and hid bill total under shipping/payment becase my shipping and payment is free so I did not wanted to display zero values
completely removed discount column because as I said before I have a webservice wich updates the prices directly so if something is cheaper it wont create a calc rule for it.
And in the plugin config I disabled preloader.
But as I said the issue appeared with a completely default system def. joomla 2.5.6, def. VM2.0.8a, def. OPC3.2
I will upload a default demo page to another subdomain and I will make you an admin user and a ftp user.