General JS-Problems with templates and jQuery

jQuery is often used by templaters and other extensions. jQuery must not be loaded more than one time. To prevent incompatibilities, you can easily switch off the loading of the virtuemart jQuery library. (Only turn off Virtuemart Jquery IF your template, or other modules are loading Jquery). This can be checked by viewing the page source.

To Disable Virtuemart jQuery
Look for this at /administrator/index.php?option=com_virtuemart&view=config tab templates.

The options for you important are:
Using the Virtuemart jQuery
Using the product Scripts (Product Scripts have to be enabled for cart functions to work)
Using the Script ajax Countries / Regions

Most jquery conflicts are fixed, when you disable the "Virtuemart jQuery" library.

Backend Menu Jquery Conflict
Slightly different, but similar is the problem, when the backend jQuery is broken. You can recognize it when the menu on the left side is completely expanded and when the store/apply has no effect. This happens, when you do not have access to the jQuery of google. So you need to prevent using the jQuery of google. But you can't store the configuration. So you must

edit the virtuemart.cfg file in /administrator/components/com_virtuemart
and change google_jquery=1 to google_jquery=0

Then go in your database and empty the table _virtuemart_adminmenuentries. Just use refresh your backend and the problem should be solved.