Pressing Ctrl-Z takes cursor to the beginning of the documen

Pressing Ctrl-Z takes cursor to the beginning of the documen

If I use the Ctrl-Z key combination to undo any changes in the active document, the last change is undone, BUT the cursor jumps to the beginning of the document. I tried using the Undo button on the toolbar. On the first click nothing happens and on the second click, the last change is undone and the cursor again jumps to the beginning of the document. I am using Maxthon browser in Win XP SP2.
sreejat