I had this same issue. Co-incidentally i had this problem on my inspiron 1545 too. I dont know if it has anything to do with it though. I too first couldn't figure out what was causing this but finally found out that it was the dell touchpad causing this issue. I just uninstalled the current one and installed an older version, the one used on 1525. And it fixed this problem. The only side effect is that you cannot see the scrolling icon when you scroll using the touchpad. Hope it helps you.