Cursor/Pointer Shadow

I have an annoying little issue with my MacBook Pro relating to the mouse cursor/pointer shadow and graphical rendering. Sometimes, after the laptop awakens from sleep (opening the lid), the shadow on the mouse cursor disappears and the edges become jaggy. Only a system reboot will return it to normal. It's a seemingly random occurrence too, sometimes it goes for days of sleeping/waking with the proper cursor appearance, other times it's the after the first time it goes to sleep after a restart.

When the cursor has gone into its "ugly" mode, when I plug in an external display, it becomes normal. As soon as I disconnect the display, it returns to its ugly self. On a couple of occasions, it's returned to normal by itself without a restart, but it's very rare.

I have a late 2009 MacBook Pro (purchased Jan 2010) running the latest Mac OS X. This bug has been annoying since 10.6.1. I always have the machine in performance mode for the graphics/power saving as 90% of the time, I'm plugged in.

Any one have any ideas? It's not a serious issue as it doesn't seem to cause any other problems, but it's just annoying and takes away from the fit and finish of operating system.