Sounds VERY familiar. Lots of devices do this, even some new laptops are like that.
It's one of those quirks of wireless, sometimes it is the WAPs fault, other times it is the wireless client's fault. We have a batch of new laptops at work which do this, if you walk out of range and come back they just stay there showing connected yet won't pass any data, sometimes takes about 2-3 minutes before they start to behave again.
You can try adjusting things to see if it helps, but often it is a compromise sort of thing. If you reduce the DHCP duration on your router when it gives out the address lease to the device if it is short enough it should mean the device will check in more frequently for new IP information and it might be enough to keep jogging it, but of course that affects your other clients. it can be caused by every sort of setting going. Wireless channel (so experiment changing between 1 6 and 11), encryption type, and other settings on your access point.
Zen 8000 Pro
Edited by Pipexer (Sat 13-Apr-13 16:26:10)