Haven't heard of it so far. What modem do you have? If the iPad has been asleep long enough, it will typically shut off wireless to save battery and reconnect on wake. Are any other wireless devices you have experiencing the same issue as the iPad?
You should try going to Settings > Wi-Fi on the iPad rather than rebooting. This should be faster, and may give better indication of what is happening.
It may be that while asleep, the iPad loses its lease to the gateway, and the assigned IP address is consumed by another device.
Note: we have not noticed a similar issue with our T1200H and iDevices.