Clutch won't engage 2nd gear.

[Sanity Clause]

Check the 4 bolts that hold the gear lever onto the gearbox housing, to make sure they're tight and not missing any!

That nylon bush at the bottom of the lever in Lipinhu's post above (p/n 33548-14010 ) can wear or even break up completely, giving a very sloppy feel.

It's worth replacing, anyway, as it's only a few euro.
Warm it up a little, and it'll fit easier. Don't forget the grease.

Do you just get the baulking when you change from 1st to 2nd? What about 3rd to 2nd?
If so, it sounds like a synchro problem.