1. Try turning SSH Keepalives on
2. Slightly OT, but I'm gonna give a shout-out to MobaXterm here, as it completely surpasses Putty as far as features go. Might want to give it a try.
3. SSH over wireless is kind of an iffy proposition; I would try a Wired connection if possible.
4. Use GNU "screen" on the remote side so you won't lose your session even if you get disconnected.
--Let us know if any of this helps...