This past weekend has been a weird one for me, I've been messing with two Dreamcasts, one of my own and one of a friend. Mine quit working two months ago, here's what happened:
At a friend's place I thought a funny smell came out of the DC fan, I don't know what it was, I identified it as a bit smokey or something, but very light. I also noticed Virtua Tennis 2 behaved oddly, and after I thought the air smelled slightly funny, I swear I saw artifacts on the textures, those you'd usually associate with a GPU overheating.
At home I decided to give it a try again a week later or so, and it started having issues I never saw before. Samba de Amigo kept resetting itself, making it unplayable. As soon as we got in the game and started shaking for a an irregular number of seconds/minutes it just reset itself. Virtua Tennis 2 fared a bit better that night. However a day later that game even started to reset itself, and after some more attempts it kept resetting during the SEGA screen and sometimes even during the swirl. I couldn't even get into the BIOS screen.
The other day my DC didn't even output an image, the only things working were the led and fan. Thus I declared it officially dead. A friend of mine who fried several of them concluded it was the motherboard where something probably fried. Could this have been the smell, of something scorching slowly? Or do you think something else might've been the case?
Fast forward two months later, yesterday I did some hardware swaps between a friend's DC and mine, more on that later. This morning I put back in my own GD Rom drive again and thought it might be fun to see what happens, you never know after all. So I hooked it up, put in Fur Fighters, and the bloody game actually started to play
I played it for 15 minutes and no crash at all, no reset whatever. Samba de Amigo was fine as well, played one game of it and saw no problems at all. Mind that I still thought what was blown out of the fan smelled funny, perhaps it's just the oil I put on the fan half a year ago, I don't know. Needless to say I'm overjoyed to see it work again, after having won an auction on ebay for a new one yesterday... Yeah, some timing 
I think it's safe to conclude that nothing burned out on the motherboard, else it wouldn't have played a game at all. Anyone recognizes this, or are you just as surprised as I am? All I can do now is hope that it will play for a longer time.
The second thing, a friend's Dreamcast. He purchased it two years ago or so, and it never really worked properly. It played some games, but crashed on a lot, or didn't boot them at all. He played Skies of Arcadia, a dodgy version, no problem with that, and the other game that works perfectly till date is Fur Fighters.
Ironically, Fur Fighters literally is the ONLY game it plays, every other game it simply refuses. It doesn't matter whether it's a backup of the game or my original disc, Fur Fighters only. Last night I tried adjusting the potentiometer on the GD drive, but had no luck. The more I went from the default setting the more I worsened it, so in the end I had to put it back to default again, so that at least Fur Fighters would play. That's when the second possible solution popped up, something that couldn't fail.
I grabbed my DC and put my GDrom drive in his DC, mine never had problems reading discs, apart from RECV and Shenmue where it would lock up occassionally. What surprised us both is that there was no difference at all compared to his laser and GD Rom drive.
None of our games worked, with the exception of the DCX import demo disc (a burned cd rom) and Fur Fighters. How can this be possible? It's not the laser, it's not the GD drive, but for some reason his Dreamcast only plays Fur Fighters and no other game. Any suggestions?
Kinda' like the whole 360 problems with overheating... Leave it alone or put a bigger fan in and bam- fixed! But, I could be wrong 
As for your friend- that's trippy!
