Clean it with a Mr. Clean type sponge, dry, and apply a coat of this http://www.castleproductsonline.com/...treatment.html in a year if you like you can repeat the process again. The NV vinyl treatment will seal up the trim and stop the running streaks that you are getting now.

 

It might be. Bought a bottle and found out that won't work in my case. I applied 303 to window trim according to instructions. No luck. Applied another coat, let stand 5 minutes, wiped dry; no effect.

Edit... obviously I judged 303 too soon. After few hours it seems that 303 has settled and no noticable "streaking" any more. Anyway, I'll repeat the treatment tomorrow.