The current instability in Southern Europe is due to the push for Kosovo Independence. Should the push move from words to deed, then a shooting war will erupt.
That would be less stable, not more.
Serbs are as capable of building IEDs as are Iraqis, by the way, a considerable problem for the current "borderless" EU.
If you haven't been to Europe lately, there are no longer border stops between the EU nations, just as there are no border stops driving from California into Nevada.
This situation includes the active ETA Basque separatists in Spain and France...a group that has contracted out their talents in the past. Ditto for November 19 in Greece and the IRA in Ireland.
Greece in particular is sensitive to the Serb cause anyway, much less if France starts bombing Serbia (which is what France wants, as Chirac's plans include breaking up NATO).
If you're worried about the Serbs and their friends, well all I can say at this point is have fun with that. The war over Kosovo has already been fought and decisively lost by Serbia, and regardless of whatever noises come out of Belgrade, they know it.
It'll remain a talking point for the Serbian Radicals until they find something else with which to try and whip their supporters into a frenzy over - my money's on the Vojvodina Hungarians.