Epson DX3800 ate my ink cartridge

[Bubo]

I don't need to do any major printing and have survived for years wthout one, but I thought I'd get the above all in one printer on a whim about a month ago. As I say I hardly print owt really, I printed a couple of photos when I first got it, and digiguide listing about a week later, its left switched off all the time otherwise. I go to print something yesterday and acording to the ink monitor its says the black cartridge is near empty, the colour ones are still full. Sure enough after a couple of pages its out of ink. I remember in the instructions it said one first use it will take up some ink to fill a reservoir but I didn't think it would take up nearly a whole black cartridge, and somehow leave the colour ones alone. Is this normal for this type of printer? Is it better to leave it switched on or something?