Mechanics and sales guys from the LBS where I bought my Trek 520 were at the bike thing at school. Three opinions I was given on my frozen freehub:
- well it's going to get warmer out
- it should be replaced
- you could take that apart yourself and clean it

Not the most helpful responses to problem that could leave me stranded in sub-freezing temperatures again. I really should have bought my bike from the other LBS. I wonder if it would be safe using a butane torch to unfreeze it, should it happen while I'm riding.

Maybe I should take their advice and have the freehub replaced as warranty work.