I don’t know which implementation of 802.11n is to blame, but the Linksys WRT610N and WAP610N both crash when a wireless client using the Atheros AR9285 causes load. It’ll work for a bit of web browsing, but stream some video or download a large file and the router will reboot.
Reflashing the router firmware (both devices are still on version 1.0), changing the MTU, and updating the Atheros driver did not make the problem go away. Brian Tillman had some luck when he replaced the Microsoft-supplied Atheros driver with one from HP, but that didn’t work for me.
I ended up switching my Xbox 360 back to a wired connection and setting my laptop with the AR9285 chipset to use 802.11g and that did the trick. Not an ideal solution, but the WAP610N I’ve got going hasn’t crashed once since then, and other 802.11n clients have worked fine.