Shipment for Virtual Products conflict in backend

[Criz]

Hi,
I use
Joomla 2.5.8
Virtuemart 2.0.XX
K2Mart / K2

Everything works fine so far but: I  added the Virtuemart Extention "Shipment for Virtual Products" created a plugin by following the instructions. Everything is fine but the Tabs in K2 backend are messed as soon as i assign the virtual product via custom field. Have you an idea how i can fix that? .

here is what firebug says:
uncaught exception: jQuery UI Tabs: Mismatching fragment identifier.

the mess starts, when I add cusom field Plug in "Shipment for Virtual Products" and a new css appears
/components/com_virtuemart/assets/css/ui/jquery.ui.theme.css

When i disconnect the custom field "Plug is" everything is fine.
I made also a clean installation on my localhost and the same happend.

I look forward to any advice. Thnk you