Eclipse cursor changes to crosshair
Solution 1:
Most likely this is the block edit mode. Try pressing Alt+Shift+A.
Solution 2:
Just so to provide solution for MAC again-
cmd + alt + A
Thanks to @vsm
Solution 3:
Clicking the 0 button while on num lock can also cause it to change...
Just wrote this incase any one else was not finding a solution! :-)