I bought the Vodafone Gateway(boost mobile phone signal at home) unit about 3 weeks ago and could not get it to work with my Belkin router, no luck with help from Vodafone or Belkin support and contacted plusnet support to see if anything could be changed at their end as the unit seemed to be unable to connect to the internet. Support were not aware of anything that would interfere with the unit working.  I was told that the Belkin and Linksys routers seemed to have most problems connecting so bought a new Netgear Unit but still no luck.
I finally found a thread on the Vodafone forum yesterday with notes on Plusnet connection issues with the Gateway. I turned off the firewall at the server as suggested and it immediately started to work.... Three weeks of frustrating help desk phone calls and £100 later.
Hope this may help someone else as it took me ages to find the solution

Thanks for the heads up, that's useful to know. We've had a few discussions about this both internally and over on the Usergroup forums. When we'd tested at our side we didn't have any problems but admittedly we didn't consider the server-side firewall