Error made on pretax medical premiums for 2007 can I get W2 corrected?

I work part time and have paid 50% of my medical premiums for the past 8 years, which has always been pretaxed. For 2007, evidentally the payroll clerk did not recieve my form to pretax my medical premiums, although I know that I signed it and turned it in. I did not know this until I recieved my W2 today. This resulted in my medical premiums being taxed. My income level is low enough that only a meager amount, if any, of my income is taxable, but this error has caused a reduction in the amount of my Earned Income Credit by about $600, since my taxable income is higher. Can payroll correct this for me and issue me a new W2 for 2007? Mistakes happen, papers get lost...don't know who to blame for this, but am upset that I'm losing money because of this error. I'm a single mom and every bit helps! This error caused me to be taxed higher all year long on withholding taxes, so I feel it can be easily reversed....can anyone help? Thanks!