have you tried a more recent kernel, pclos3 perhaps?
about the N, is it transmitting on N only or abgN mode?
maybe the problem is the router and not the machine
my netbook works in N on winxp, 150mbps
in linux i am not sure, but it works withotu any problem while being the router set to work on abgN, i'm sure because i forgot the router password last week and had to reset it and reconfigure everything