Whilst pushing a recent commit on SparkleXRM I recieved the following error:
An error was raised by libgit2. Category = Net (Error). Error while copying content to a stream.
I turned it off again (rebooted), and used fiddler to trace what was going with no luck. In a last ditch attempt I changed the networking on my virtual machine from NAT to Bridged and hey presto it worked agiain.
So it seems that Git doesn't like NATed connections from Virtual Machines.
Hope this helps someone else!