SILICONE!take the tyre back off and the rim tape and silicone all the way around where the rim tape should go. put extra on where the spokes are and refit the valve and put loads under and around that,then put your rim tape on whilst the silicone is still wet. wipe off any execess. leave it to dry over a couple of days and then refit your tyre. if this does not work try a new valve and re silicone. if this does not work then you probably have a puncture. the silicone trick worked for me only last week, although i fitted a brand new rim tape and valve. to make there is no water coming from around the valve and spoke are spit onto your thumb and finger, not a greeny though as they don't work, just rub it around the spokes and valve but you need quite alot, and just watch for any bubble, if non appear then it's obviously a puncture. hope i've helped chris.