Can't save Configuration Shipment Method

I have another problem in Virtuemart.
When I add a Shipment Method only the Shipment Method Information is saved while the Configuration is not saved, it is all blanks.
What I have to do ?


Thanks in advance, bye

sviluppo.sistemide.it/z-propashop
Joomla! 2.5.19
Virtuemart 2.0.24

I add a detail:

If I select VM - Shipment, By weight, ZIP and countries as Shipping Method in Shipment Method Information it doesn't work

It works only if I select VM - Shipper, By weight, ZIP and countries as Shipping Method in Shipment Method Information

Try to update to vm2.6

Do You think it is safe ?

Make backup first (site files and db)

OK ... I'll try

Bye