According to this, based on a RIA Novosti report, Abkhazia has entered the fray in the Kodori Gorge area, which is at the old cease-fire line and was the site of the last flare-up of Georgian-Abkhaz tensions two years ago.  The AP confirms Abkhaz involvement.  Foreign Policy‘s blog reports the comments that the Abkhaz foreign minister made to Der Spiegel.  Abkhazia’s entry into the war may have been unavoidable, but I think that may mean paradoxically that the conflict will take longer to resolve now that a fourth party has joined.  It should hasten the end of hostilities by dividing Georgian resources, but it could complicate arranging a cease-fire.