Running 141 and 512, and no wifi problems, even while sleeping.
Silly question, but under the wifi advanced setting, there is an option for when to keep the radio awake... Make sure this is set to "always", and not sleep with screen off.
Sorry if you already knew, just something to try... I noticed after a factory reset it always defaults to sleep with screen off
Sent from my Galaxy Nexus Toro - BB 404