Fence on Neighbors property

8 years ago I put up a fence in my backyard. All of my neighbors agreed on where it should be placed. One neighbor subsequently moved and the survey done for the buyer's mortgage co. revealed the fence to encroach on the property, much to my surpirse. I and the buyer of the adjacent property signed an agreement that they had no problem with the encroachment. To this day I am not sure that the survey was done correctly, as I compared it to my plat. I forgot all about this and have since sold my house. Am I liable for any damages for not disclosing this to the buyer of my house even though the neighbor agreed to accept the encroachment?

I am having a similiar problem with an existing building that was on my property when I bought it in 1987. The people we sold the property to are now sueing us because they said we did not tell them of this problem when they purchased it. I am also wondering if we will be liable.