I think malpractice is more for causing bodily/psychological harm or death. Being stuck with a bill your doctor's office is unwilling to foot seems more like a small claims court deal. I'd check with a lawyer, though.
I have had issues with my doctor's office screwing up my claims. Has the insurance company refused to pay? I called mine up and was told that they would pay if the claim was resubmitted with the correct information. Of course it was for services I had been receiving with the same diagnosis for a year, and there was no reason for those claims to randomly deviate like they did.
Definitely call the insurance company if you haven't already. If the doctor's office screwed up, make sure to point that out to the insurance folks. Insurance companies don't like to contract with doctors who mess up.

