Are you *sure* it's the employer's fault? I'm not a lawyer, but I work in a payroll office and it's absolutely amazing to me how much gets blamed on payroll for underwithholding. So we dig through the files and lo and behold we are withholding at the rate requested by the employee.
One of the more common issues sounding similar to yours is where an employee will claim the same number of allowances for federal and state. It might work out for the federal, but on the state side, not enough money is being made and the allowances cancel out the withholding.
I can't answer for definite because I don't have the training necessary to go further than basics... But I would double-check your allowances and if necessary change the federal and/or state.
Oh, and I also wouldn't be so quick to lay the blame on your employer because it is your responsibilty to be sure the deductions on your stub look appropriate. You should have noticed in January of last year that there wasn't state tax being taken out. You are partly to blame because you ignored your stub and didn't take appropriate corrective action (like filling out a state form) when necessary, rather waiting until the tax year was over and nothing can be done except to deal with the consequence.
I do apologize if I sound a little harsh... Tax season can be mean on poor, innocent payroll clerks.
Good luck!