I have a MX mouse, one of their first good wireless ones. Very good normally but sometimes if you put a glass in front of the receiver it can get jumpy.
Not sure if you have the wireless one, maybe post up some pics of your setup that might show some incidental detail that is the cause.
Otherwise just search for someone using the same mouse with the same mat or contact the mat people even and ask them
In ye olde days I would have wondered about driver or irq conflicts. Its always worth changing options or altering setup to see if anything helps, uninstall, reinstall and so on
Otherwise is there such a thing as spray on teflon ? Mat probably needs either some wear in or some kind of coating might help