Georgia broke away from Russia in 1991 (1), and the international community recognized Georgia as a legitimate country. South Ossetia has had de-facto independence for more than a decade (they entered into a sort of cease-fire agreement with Georgia in 1992 (2)), but has not been recognized by the international community as an independent nation.
It seems a odd (not to mention hypocritical) that we've been hearing near-universal condemnation of Russia (which I agree with), but Georgia somehow always seems to be portrayed as the good guys, just defending their territorial integrity from the evil Russians (and to be fair, the Russians have far exceeded their stated purpose of defending South Ossetia). But Georgia has only really had control of South Ossetia for about a year. Why should Russia's actions against Georgia be treated as aggression and not Georgia's actions against South Ossetia?
(I am not an expert on international relations, so if I'm oversimplifying things, please feel free to correct me.)
1 http://en.wikipedia.org/wiki/Georgia_(country)#Restoration_of_independence
2 http://en.wikipedia.org/wiki/South_ossetia#1989-2008
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