Republicans pretty much wrote the Senate Finance Committee bill they now won't support.
Lots more info at Crooks and Liars
As dday says:
Republicans don't like it because... it's a health care bill. Democrats don't like it because... it's a bad health care bill designed to kowtow to Republicans who won't even vote for it. Health care advocacy groups don't like it because it "would give a government-subsidized monopoly to the private insurance industry to sell their most profitable plans - high-deductible insurance - without having to face competition from a public health insurer." A good reason not to like it! And unions don't like it because there's no employer mandate and it would "tax health plans."