I'm new here so this may be an old question. The equivalence principle states (roughly) that one can't distinguish between an accelerating frame and a uniform gravitational field. But an accelerated charged particle radiates. Thus the EP seems to imply that a stationary charged particle in a gravitational field will radiate, but this doesn't happen. The other possibility is that an observer in a frame accelerating along with a charged particle sees no radiation. This seems reasonable, but this question still seems to be the subject of active debate. The question appears to boil down to whether radiation is frame independent (i.e., seen by all observers) or frame dependent (not seen by an accelerated observer). The latter view is advanced in a paper by Shariati in Found. Phys. Lett. 2 (1999) 427–439, entitled "Equivalence principle and radiation by a uniformly accelerated charge" and the former view is held by Parrott in his paper "Radiation from a uniformly accelerated charge and the equivalence principle" in Found. Phys. 32 (2002) 407-440. This guy claims that the EP fails for charged particles. Any ideas on who is right?