You may encounter the following situation:
After selecting a drawing tool, the mouse cursor does not refresh properly and displays the cursor as an arrow instead of as crosshairs. This makes drawing quite tedious as the stroke appears from the middle of the arrow instead of at it's tip.
This is most likely caused by a theme you are using which modifies the size or look of the cursor.
You should be able to remedy this by reverting to the default theme, Control Panel > Mouse > Pointers tab and selecting (None). This should refresh your mouse cursor.
Try running the software afterwards to see if you get a better behaviour. You may be able to revert back to your old theme once the cursor refreshes correctly.
Mac OS X (all)