You should not compare Colonial with RBC... First, RBC is not negociating under the gun. Second, i dont beleive your 1.3 B mark down. Finaly, PNC will very likely make a competitive bid and dont rule out USB or STI.
Price movement in the last few days are more linked with the politics around the US deficit and debt seiling. The elected clowns (both republicans and democrats) are not understanding the real outcomes. International investors are staying away of US markets (or shorting) and this will continue until these outcomes are clarified.
There are also many corporate decisions that are stalled right now just because of these uncertainties and this is extremely bad for US economy. Expect a long time frame before any deal concerning RBC.