Velocity is automatically changing in List editor

Hope someone can help me. I have been using cubase 5 for quite a while with no issues, but recently reinstalled it onto my Windows 7 laptop. Now whenever I go into list editor to individually change the velocity on certain notes, I left click in the data field and the velocity automatically changes to 100, and to edit it I have to right click in the field then drag the mouse over the value to reset it. In the past all I did was left click, the value in the date field stayed the same but I could type in a new value. Any suggestions would be most appreciated, probably something really simple I am overlooking