Can you describe the smell?
Dirty socks? Armpit? Dog poop? A wino's breath? Something unrecognizable left in the fridge for way too long?
Like a slight vanilla mixed with old book, but mostly moist basement smell.
For some reason the link doesn't work for me. What kind of guitar is it?
S-100 http://imgur.com/a/JzXYq
I would try an ozone generator, if I could rent one or borrow someone else'. You could also get a couple of replacement HB-1s from the Guild store. You might like those better. also, your link seems to be bad.
Link fixed http://imgur.com/a/JzXYq
With basement storage and decaying case I would be concerned about mold spores that can be a serious health hazard. I would wipe the guitar down with diluted chlorine bleach, dry it well, and let it air dry for a few days before setting and stringing it up again. Discard the case.
Would an ozone generator kill them?