What does it mean when a lawyer accepts your case then sends a letter in the mail advising that he cannot accept your case?

I was in a car accident I was operating a 50cc scooter and was making a left turn I was hit by a car. Neither of us,the drivers was given a ticket. I was driver number 2. My collar bone was broken. I hired a lawyer that accepted my case on contengency. The investigator came to my job, ask me some questions all hospital records were given to the firm including missed days from work I even went to the lawyers office and met with the other parties insurance ajuster along with a person that was suppose to be representing me. About two weeks later I recieved a letter in the mail from my attorneys office stating that they could no longer represent me due to confusing curcumstances, but I had a period of two years to take the case back to court. What went wrong with this case???????!!!!!!!..