I can't concur that one...
Loosening an IDE cable could easily do it. Doesn't that suck?
It happened on my old computer. I installed an IDE CD-RW in my Cyrix 6x86-P150+ (mistake), and I loosened the cable to the first IDE hard drive. Then, I got NOTHING on the monitor.
I didn't think that was possible, so I had a friend look at it. Sure enough, that was the problem. It's pretty sad, isn't it? I probably could have figured it out eventually, but I am impatient and I jump to conclusions faster than shaken pop bottles build tension.
Anything can affect anything IMHO. Just take caution in what you're connecting.