Funny you guys are still meddling with clear cmos; I've never had to touch that thing for probably the last two years or so. With this board and some memories, usually, pulling one ram stick can do the trick (no not a voltage thing), but I mostly use the reset swicth; just hit it continually (like 6 times) for very tough situations like yours; that usually forces a hard reset (system shuts off completely, then powers back on) and I'm usually able to go back into bios. If you're running multiple HDs and you find yourself staring at the ICH boot screen, give it some time, usually it takes a while for the HDs to be re-detected. Sometimes, while stuck during post, pressing power-on button for about 5 seconds and forcing a shutdown can do the trick.

Generally speaking, when moving to water, you have to readjust all voltages because as watercooled chips get cooler and usually need less voltage, stuff like NB, ICH, and mosfets suffer because they no longer get secondary air from the cpu HSF. Unless you're actually cooling these, I'll recommend paying attention to those. I also strongly suspect what zsamz said.

By the way, you mean etcetera, not "exedra."