Lime-green screen of death!

I was done for the day, I used Mac Janitor for the daily & weekly cleaning, then I re-started. I don't remember if I logged in or not. (to my computer) Yesterday (the next) morning, I "wake it up" so I can check my E-mail & my screen is a solid lime green! Nothing I did with the mouse or keyboard would change this, so I re-started. Actually, I had to shut it off. I waited about a minute & when I turned it back on, the speaker beeped 3 times & the white power light came on for a second and then blinked 3 times. The light repeated this every 30 seconds or so. My monitor wouldn't come on, no lights came on on my keyboard or mouse. Nothing worked. I shut it off, unplugged the tower. Came back after a shower to find more of the same, except the light would now flash very quickly before & after the 3 "blinks". i.e; On for a sec, flash, blink, blink, blink, flash. Pause & repeat. I shut it off, unplugged it, took out the battery & RAM (old PC trick). Left for the day. That night, everything back in & on. Exact same results. I saw in a thread somewhere that the tones & light is some king of code, but I have no idea where. I've been using Camino with no problems, but I just started a Nightly Builds membership. If I did log on after I re-started that first night, I wouldn't have left the browser open. I'm really at a loss here and could use some help.