Will try to cut to the chase on this. I was going through a divorce in 2006. I hired and paid for my attorney. My ex-wife hired her own attorney. In our divorce, we agreed to sell the house and split the money/

I went to my ex wife a few weeks after the divorce and asked her if I could pay her 35K to move on with her life. I have a special needs child and didn't want to uproot him. She agreed. I cut her a check and she moved on... A year after the divorce, I remarried and placed my current wife's name on the deed of my home.
I did this via Quitclaim deed (no title search)

Fast forward to Sept 2012... I went to refinance my home, to find out I have a lien on it. My ex-wife's attorney placed a charging lien on the property. I went to the courthouse and received the "Notice of Charging Lien". It was notarized and signed. But under where it says "Certificate of Service" (certifying that a copy was sent to my attorney) it is not signed.

My attorney searched my file and could not find this notice. I spoke with my ex-wife and she "had no idea" how this occurred.

What should I do?

Did your ex ever sign a quit claim?

But you go to your ex-wife's attorney and ask him to release the lien. If he refuses then you have to decide your next step, which will probably be to file suit to release the lien.

Did your ex ever sign a quit claim?

But you go to your ex-wife's attorney and ask him to release the lien. If he refuses then you have to decide your next step, which will probably be to file suit to release the lien.

My ex did sign the Quitclaim deed. I'm at a lost.

I did go to my ex's attorney and asked that it be removed.. No dice. My only out on this might be that the attorney was to give me (via attorney) notice of this.

Although, it appears she filed it, Certificate of Service isn't signed.

What is the attorney's grounds for the lien?

The lack of signature is not going to help you. If there are valid grounds for the lien, then it will be upheld. So you need to find our the grounds for the lien and fight it on that basis.