GUI lag after slicing drum tracks

Hi, I have recently upgraded from Cubase 5 to 7.5. I have been a happy Cubase user since day 1 of my production journey. But this is the issue i am facing while editing multi track drums. After slicing the drum tracks there seems to be a lag with the GUI while zooming in and out and scrolling. While this is nothing major but it does make editing a little slower. Any idea why this lag is happening?