|It could be the type of mouse mat you're using, especially if it has a shiny surface or a picture on it. Optical mice can't track properly on some types of surfaces. I use my optical mouse directly on my desk top which has a woodgrain effect. The mouse tracks properly with no issues at all on that.|
It also works fine on a uniform matte black or gray, fabric mouse mat, but not on mouse mats which have a shiny picture on them.
Suggest you remove the mouse mat and try using the mouse without a mat at all.