Background: For work I routinely need to connect to a secure VPN that is completely isolated from the internet. When using it, I can only connect to the servers that reside within the network and the VPN software (Cisco AnyConnect + NAC Agent) seems to automatically redirect all http requests to external sites to a catch-all 'sorry you can't do that' page.

So while connected to the VPN, Firefox Sync doesn't work and nor do I expect it to. However, my issue is that every time I connect to the VPN, Firefox silently pops up a "sync encountered an error while syncing" error message bar at the bottom of the browser, which I have to manually close. This obviously isn't the end of the world, but having to do it all the time gets annoying so I was wondering if there was a way of suppressing that particular error message or maybe getting Sync to handle the secure VPN more gracefully.