Limited or no connectivity within SP2

I've got an 60 AP 802.1x peap site install where we were having alot of
problems with the above error during operation.

We removed the APs and replaced them with another make. The problem has got
better but still every now and again the above error appears.

It seams to appear either at the edge of the wireless cloud or in the middle
if there is obvious AP overlap. The APs have logic within them to space the
channels out correctly and I can confirm the channels are ok.

Reading the docs it means that an IP addresses couldn't be requested. On the
basis that the APs have been replaced it either means that its bad luck and
theres still a fault in the APs, that the not dhcp server is not replying to
requests for some reason or that theres a fault with the SP2 zero wireless
config service.

Has anyone seen the fault before?

Tim