Not that it matters now, but all you needed to do was perform a firmware update. The below will be helpful for anyone coming across this discussion (via the support pages at www.plus.net):
The 585v8 v8.2.7.7 firmware is known to cause wi-fi connectivity problems with certain Apple computers. To fix this problem we recommend that you upgrade to v8.2.7.8 that features updated wi-fi drivers from the chipset manufacturer. No official upgrade tool exists for Apple computers so you may need to reflash the firmware using a Windows computer instead.
I did this yesterday and it fixed all of the issues I was having - no Airplay icons, cycling for wifi networks, dropped connections - all of these righted themselves after a firmware update.