The AMPTP walked away from the table.

From AP:

"With SAG's continued adherence to unreasonable demands in both new and traditional media, continuing negotiations at this time does not make sense," the producers said in a statement.

The guild responded in a statement by saying the producers' decision to end talks after 18 days was unfortunate.

Nikki Finke puts it like this:

A favorite negotiating tactic of Nick Counter's is to repeatedly offer nothing new until each guild is forced to negotiate against itself by continually reducing its demands. This is exactly what was done here. Already, just in three weeks' time, SAG has softened its proposals: for instance, it's agreed not to double residuals from DVD sales, instead asking for what would effectively be a 15% hike in DVD pay, as well as scaled back its 50% pay increase for guest stars on TV shows.

How incompetent do you have to be to cause two major strikes within a few months time? Incompetent enough to work for the government. Err...run the government.