Having now read it - I was following on Bing maps as well - the minute I realised you were heading for that path up from Loch Treig through the Lairig Leacach, I went "Oh, no..." I've done the whole of that path, with a loaded mountain bike. We had to push more or less all the way from Loch Treig to the Lairig Leacach bothy (where the path meets the track). From there it is a fast and easy downhill all the way to Spean Bridge.
Pedantic moment - I don't think the mountains in your photo are Ben Nevis. I think that is Aonach Beag and Stob Coire Bhealaich, hiding Ben Nevis behind them.