I've had a similar problems with my Phoenix 1000 board. With FPU installed I get flashing power LED and black-grey-white screen in a loop.
Unfortunately I'm yet to acquire another FPU to test and I don't have anything else to try the FPU in, so I don't know if the FPU is dodgy or something else is at fault.
Seeing someone else with similar symptoms on different hardware though, makes me think that maybe we both have dodgy FPU's as that's the only common thing between them.
And personally I'd try running it at stock speed until you can discount the overclocking as the source of the problem - if your clock crystal is socketed I'd pick up a 40MHz or 33MHz one from the local electronics shop, swap it over and see if that makes any difference (or if the 33MHz FPU works too).
