Sleep mode problems with external Monitor After the latest update (10.8.3), I encountered a problem. When my external Acer monitor is connected (via HDMI) while trying to put my MacBook Pro into sleep mode, everything works fine. But suddenly, after a few seconds, the HDD seems to wake up (I think its the HDD because of the noise) and to sleep again and wake up again. This happens all the time in 10-20 sec. time intervals. Furthermore, this only happens when the monitor is in standby. When I turn off the monitor via key or unplug the cable, the HDD stays in sleep mode. It seems like it's sending some data, which prevents the MacBook from going completely into sleep mode. I also connected it to my TV. There were no problems when connected to the TV. It seems like it's only happening with the Acer monitor.

Any suggestions how to fix this?
Can you open console after that and search for "wake"?
There should be something like "kernel: Wake reason: "
I think it may give a hint.

PS sorry, don't have enough rep to post it as comment