a few things to try,one try hitting the SCROLL/LOCK key on your computers keyboard.sometime this gets hit by mistake.
also when making edits on the fly in x2 scroll will freeze by default,this is normal behavior.
simply go to the nowtime/timline and right click when you see the magnifying glass.
this resets scroll lock.
there is also a preference in the track view settings under views.not global settings either/track view settings.
either of these 3 will solve your issue.
though you didnt mention what view you are having this problem in,if its piano roll view.
the same settings apply.
Charlie