From YahooNews:

US debt clock running out of time, space

NEW YORK (AFP) - Tick, 20,000 dollars, tock, another 20,000 dollars

So rapid is the rise of the US national debt, that the last four digits of a giant digital signboard counting the moving total near New York’s Times Square move in seemingly random increments as they struggle to keep pace

(more here)

Maybe they can just borrow some money to build an extra digit, or a new sign.