Address space error when creating new virtual machine

Hi,

I'm trying to create new VM in our virtual Network but GUI gives us error:

"Unable to allocate the required address spaces for the deployment in a new or predefined subnet that is contained within the specified virtual network. The long running operation tracking ID was: 328a6db2a961851291d9c471a5ed8dd7."

Tried to delete Virtual Network but cannot do that because GUI says that Network would be in use. I cannot find from GUI anything which would use Network.

Any thoughts?