No experience with that router, but easy things to try first (things I have done for speed issues with my Netgear WNDR3700 which is similar):
1) I would first check that QoS is disabled (if enabled, may be throttling bandwidth)
2) Maybe change the channel your router is on as it maybe interfering with other routers or wireless gear close by. Change it to like channel 8 or something different than 1 or 2.
3) Good practice, but not necessarily related to the issue...I had experienced page time outs, etc. in the past using my provider's settings. To cure it, I changed my static DNS settings in the DHCP network settings to Google's:
Static DNS 1: 8.8.8.8
Static DNS 1: 8.8.4.4
4) After doing the above - on the Mac gear, maybe try turning off their wireless adapter, deleting and then reinstall it with a different name.
Other than that try support and or support forums. Make sure your firmware is up to date, but also make sure you know the correct firmware and procedure for flashing because it's easy to brick a router.