My brother used to race for the Sobe/Cannondale squad back in the day. I presume its a headshock ultra your talkin about. In less than one season his forks would do that. Between the Cannondale wrench in town, Cannondale themselves and as a last resort (I seem to have a following for fork rebuilding) We couldnt get it to stop leaking consider almost everything was new. It took an entire new front end to stop it.
Its just the draw back of having one of those frames witch is a shame because they are quite nice! I would try this. I do attach a warning that its a last resort fix and may only last you part of a season. Its an old motocross trick. Flip the bike upside down, remove the core from the schrader valve and inject 10 cc's or so of an oil that has an active seal sweller. Alot of ATF fluids will work too. Whatever you use it must have a lubricating factor to it! Replace the valve, Inflate to needed pressure and go for a little ride where the fork is going to see some action. re check your pressure and let it sit for a few days.
It just goes to show no matter how complicated and modern any suspension claims to be you can hack any of it back together for one last chance! So far in my 4 years of racing DH im up to rebuilding 2 rear shocks with cooking oil, using bits of rubbermaid lids as valves and glide rings, and using a cut off handlebar to cover the bottom of a cartridge that cracked. Now that was sheer genious!