Heat issues? Look here

I've been having my Unibody run pretty hot the last couple of months. CPU and Heatsink A at ~77 deg according to iStat Pro. And this without having any CPU load (believe me, I have checked for runaway processes and stuff like that).
Suddenly I got thinking that this hotness might have corresponded with my adding extra RAM. My guess was not the RAM itself but that I might have reseated something while meddling inside the case.

So I unscrewed it again and just had a look around, blew away some dust around the fan, saw nothing out of the ordinary, and put the cover back. And hey presto, now my temps are at 43 deg. I don't think I ever saw a temp like that during the last six months.

I have no idea what might have been at fault, or what got corrected (?) It might be a bit early to conclude anything, I'll post an update in a couple of days. Just wondering if anybody might have had similar experiences?

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Update: 55-67 deg after some flash video playing, fan at 2000 rpm. Previously it would have been 77 and 4300, respectively. Something has happened...

Message was edited by: SwedePetter