It's tough being a man new to the swinging world... For that reason we try to always have some Viagra/Cialis around when swinging. It happens to even the most experienced swinger guys sometimes.
Personally I like Cialis more, works like a charm, and lasts for 36 hours (more like 3 days sometimes)
But it IS a huge blow to the ego, took me a long enough time to get over it. So I have a pretty good idea what he's going through. Only thing to do is to support him plenty and he'll be ok.