To fix this, you need to open your Vista documents folder. (Default is c:/Users/
Once in the default folder (or whatever you named your profile) right click on actionmaps.xml and choose open with, and then select Notepad.
Once you have this file open, scroll down and look for:
action name="attack2" onPress="1" onRelease="1"
Go ahead and change "mouse2" to whatever key you assigned zoom to, or to whatever key you wish.
Click file at the top and save.
Now you can rock dual SMGs without any weird secondary behavior. (Jumping every time you shoot sucks!)