I had the same problem until changing the wifi radio to 100mW and medium for power saving. Connection issues went away.

I have two N900's right now and both have the same issue with my G/N dual band Netgear router.

Sending the second one back this week (was supposed to replace my current N900, but same issues PLUS the second one reboots randomly). Definite device issue, since no apps were install to the second one. Just what came with it.