According to this document :
http://cool.conservation-us.org/coolaic ... 11-33.htmlGore Tex is resistant to Hydrogen peroxide.
This from a tent maintenance site :
"To remove mould or mildew, make a 5% solution of hydrogen peroxide. (125ml in 5 litres of water.) Sponge the solution on and, when the mould is gone, rinse off and wash the tent as below. "
So you may want to patch test that to see if it works.
First thing I would wash it according to the instructions here :.
http://www.gore-tex.com/remote/Satellit ... structionsFranco