Optimism over Fed Chairman Bernanke's comments on Wednesday faded as global markets sputtered over unsettled Greece woes.

Futures on the S&P 500 Index fell 1.00 percent and futures on the Dow Jones Industrial Average fell 0.71 percent at 8:43 am EST. 

The German DAX is down 0.16 percent and the U.K. FTSE 100 is down 0.51 percent. 

Commodities generally fell, with copper falling 1.56 percent and crude oil plunging 1.75 percent.

Two troubling developments about Greece unsettled investors.

On Wednesday, tens of thousands of protestors took to the streets to protest against the austerity measures.  There were also reports of rioting and clashes between police and demonstrators.

S&P, the rating agency, also threatened to further slash its rating on Greece sovereign debt. 

The agency stated that uncertainty over public support for the austerity measures and over Greece's economic growth prospect cast serious doubt on the country's ability to implement its budget cutting and tax raising plans.

Higher than expected unemployment claims for the U.S. and lower than expected core durable goods orders were also reported at 8:30 am EST.

The disappointing data sent the S&P 500 futures down further. 

Market participants are also eyeing President Obama's televised healthcare reform summit and Fed Chairman Ben Bernanke's second day of testimony before the House Financial Services Committee.

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