When the Tab is trying to Obtain the IP address do a soft reset by placing a pin into the reset hole. Do this only when it is trying to obtain the ip address. Do it three times and you should be fine.
I've tried that several times to no avail.
Basically, the only way for me to connect my Iconia to wifi for the first time (or when the tablet wakes up) is to reset my router. At that point it shows "connected" Until then it just keeps trying to "obtain IP address" Nothing else works. Not a soft reset, not forgetting and then re-connecting to network etc.
This only seems to be an issue on secured networks like at home. When I took my Iconia to work, it immediately connected on the unsecured network.