Try talcum powder - really!
Nope, no dice, and my skills to get things clean (and the resources I have access to in order to achieve that ) are a bit beyond average.
I know what Alistair is speaking about because it happened to me a couple of weeks ago myself - I was just unaware that it was the pen rather than something I did myself during my travels.
As I move around a lot (geographically), I have bits of kit scattered in various places and it means I thus don't see kit for months, as was indeed the case with the Bamboo tablet. My need for a digitiser is pretty much taken over by an iPad (with a Wacom pressure sensitive pen) although that may not last because it's apparently illegal to provide a pen tip thinner than a broom handle or stiffer than a cheap sponge. Although there is *potential* for better accuracy, everyone seems to be going out of their way to prevent end users from getting that. But I digress.
It was as if I'd stored the stylus near some very old tape that had since decided to decompose, like the stuff that remains on your suitcase after you peel off airport labels, or the crap that remains in your passport after yet another idiot decides that sticking a luggage ticket inside an expensive ID document you need to keep functional for years is the right way to make you happy. Thankfully they have not yet resorted to sticking it to my smartphone which holds the ticket, but that's because I reclaim that before the temptation even begins to form. I wonder what these people do at home.
I know a reasonable amount about materials, surfaces and how to keep them clean (which is why people with matte paint on their cars amuse me), so I sighed and tried to clean it off. Which isn't possible. Well, it isn't possible if your definition of cleaning involves getting to a stage where it will not spontaneously glue itself to whatever it touches. If you favour the now more improved "grip" I'm happy for you, and please don't ever come near me again.
In the end I did the only thing I could do as a faithful consumer.
I threw the whole thing away.