I bought a used canon 20d a few weeks ago and for a while it worked fine and I was really liking it. The problems started the second day of a dance weekend about a month ago. I shot about a hundred pictures the previous day and all was well. The next morning I pulled it out, put on the flash just a before. When I clicked the button, the mirror acted normal, but it immediately went to an error 99 state. I tried taking the card out, and taking the battery out and letting the capacitors drain, and then putting it back in. But nothing worked. After a couple hours of trying it every few minutes it started working fine and had no problems the rest of the weekend. The biggest episode however was a couple weekends ago at a d-day concert and display. It would not work at all no matter what I did. Well, to be fair, it worked for about half an hour in the middle of the day but not before nor after. Nothing. Not able to record a single picture. Every time it gets and error 99. I've tried it once since then, and it took one picture then locked up again. I don't think its the card, it can display pictures you've already taken, and it acts that way will all three cards I have, from two different manufacturers and different capacities. It doesn't seem to be the battery, everything is powered fine. The firmware is the latest version I think, 2.3 something. If it's important I can look and tell you exactly. So what is wrong with this camera? It doesn't like moderate heat? It doesn't like outdoors? (but the dance event was indoors although it was warm) Is this a common phenomena with all 20d's (if so, how in the world did they sell any at all)? I want to like it. I really liked my rebel 2k film I had for ten yrs or so. But if this can't be solved I might as well throw it in the river. Frustration is running high. Thanks for the help!