Probably yeah, though I had checked our connection priorities amongst many other things and couldn't make out why it was getting in the way. Nothing had been changed in hamachi recently, but then I remembered I'd had a similar problem with another game in the past, and hamachi was the cause so I deleted it and low and behold, problem fixed.
I just seem to have bad luck with hamachi, after not changing anything for weeks it suddely screwed the pooch, hasn't been the same since they were bought out 