Hi ,
i would like to suggest the use of a single version of jQuery for virtuemart configuration, now if you chose "Using the VirtueMart jQuery" only, the version 1.6.1 is added to the head but if you choose also "Use external google jQuery library" version 1.8.1 is is added to the head.
As version 1.6.1 is very old it is causing issues with many extensions and templates also, it would be easier and less confusing for the end user to always load the same version of jQuery.