Thanks! A Knytt in Time works fine for me. However, the bug about the Double Jump after an updraft is still there; it's not that bad, though, as there are very few levels relying on that kind of jump (I only remember a couple, and they're very old).
P.S: after looking at the code, I couldn't figure out what's wrong; it's probably a call to _ds_juni_change() with the 'reset' flag set (ds_juni.c, line 64), since any other function that resets ds_global_juni.inDblJump seems ok.