Whenever my mbp 15" 10.6.8 goes sluggish (which happens from time to time as I never turn it off and re-boot, only sleep it) or things in general don't work as they are supposed to, I start the terminal app and key in a sudo command that I will come to later. This command will clean out your system from a lot of garbage that it does not need. Usually some of it is taken care of automatically by the system itself, but only when the computer is started and/or at 3 o'clock in the morning once a week and once a month. But most people don't have their computers sitting idle at 3am on their desktop - they are most likely sleeping, like their owners.
Important to notice when you do this operation is that you key in the script exactly as written. The reason is as you are giving your computer a sudo command, you are digging around in the inner core of your computer and you don't want to tell it do something that you regret later.
Ok, here it goes - and yes, it solved my Flash not working in Safari problem.
1. Open Terminal, located in the Macintosh HD > Applications > Utilities folder.
2. At the Terminal prompt, type the following, exactly as written:
sudo periodic daily weekly monthly
3. Press Return.
4. Type your Admin password when prompted, then press Return.
All three scripts will run in sequence. There is no visual feedback while the scripts execute. You will know they are completed when the Terminal prompt returns.
If you want to know more about maintenance scripts for OSX, go here
http://www.thexlab.com/faqs/maintscripts.html#Anchor-Manually-49575