PC Not Booting Until a Different Phase is Used?

2by4 asks: "I run at IT Dept for a small firm, our network room houses production & development servers. Some machines are plugged straight into a strip with no UPS. Here is the Mystery Problem: When the power glitches, the strip machines go down, and some of these machine WILL NOT come up again until I switch them to a new outlet. Once this happens, I can put them back on the original outlet and they will work. Unplugging & replugging on same outlet is not enough. I have seen this on at least 5 machines so far, with independent confirmation. We can narrow the 'fix' to plugging into an outlet of a different phase (there are 3 separate 120v phases powering the room). The symptoms vary from no powerup, to frozen at the BIOS (depends on motherboard make), etc, but consistently, switching to a new phase fixes them. I tried the 'unplug-wait-&-replug' cycle, to no avail. Using a new outlet w/ a different phase is the only solution. Any theories? I assume the new phase is causing something to 'reset', but what? I can provide more details, but I am wondering if anyone has seen this before? I am completely and absolutely stumped. Our power is healthy, lightly loaded, evenly distributed and the power strips are new. I know I should have at least a simple UPS, but this mystery is causing me to lose sleep."