Soapy water has always removed 505 over spray for me.
I agree with Karen. 505 Spray and Fix brand adhesive is a temporary adhesive that is water soluble, intended to wash out completely when you wash your quilts. Just try washing your cutting mat with a damp wash cloth dipped in sudsy water. Should work!
Linda -its not the number of breaths you take, but the moments that take your breath away!