@OP
You're not alone. Other people with Maxx's are having the same issue. See
https://forums.motorola.com/posts/ccc0b71008?start=106&stop=120#615620 and
https://forums.motorola.com/posts/2d2211eaeb?start=1&stop=15#615623
It's not your router, it's the phone. I was using wifi no problem yesterday, 6/14/12, before I updated my software version last night from .173 to .181 because my gf's Maxx could not access the wifi.
Hopefully by posting enough we'll get enough attention from Motorola and they'll fix it. Otherwise, try the workaround in the second link. It worked okay for me, but it's still much slower than the 4g LTE and the speed I was browsing yesterday on my same wifi (same everything in fact, save software vesion).