First, uninstall Flash: http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html
Follow the instructions carefully.
Then, install Flash: http://get.adobe.com/flashplayer/
... Safari quit working, but for some reason, only for my main user account.
If Safari is misbehaving only for your account, you can try several remedies in the following order:
Reset Safari: Safari menu. Check all the boxes that appear relevant.
Clear Safari's cache: Depending on your version of Safari, that may be in the Safari menu. If it is not there, then go to Safari's Preferences > Advanced, and enable the Develop menu. "Empty Caches" will appear in the Develop menu.
IF that does not fix things, then there is some other problem with your user account. Check your login items and whatever third party programs you may have installed. In particular, uninstall any and all third party "anti-virus" or similar snake oil utilities.
Next problem: Problems related to fans, power, or sleep all justify an SMC reset:
Resetting the SMC on Mac portables with a battery you can remove
- Shut down the computer.
- Disconnect the MagSafe power adapter from the computer, if it's connected.
- Remove the battery (to remove the battery - click here: MacBook or MacBook Pro).
- Press and hold the power button for 5 seconds.
- Release the power button.
- Reconnect the battery and MagSafe power adapter.
- Press the power button to turn on the computer.
Resetting the SMC on portables with a battery you should not remove on your own
- Shut down the computer.
- Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
- On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
- Release all the keys and the power button at the same time.
- Press the power button to turn on the computer.
Next problem: if your Mac is not automatically joining your home Wi-Fi, try this: Turn off AirPort from the AirPort icon. Then go to System Preferences > Network > Wi-Fi > Advanced button. Remove any networks that are "remembered" but leave the box "Remember networks this computer has joined" checked. Click OK, then Apply. Turn on AirPort in the AirPort icon, then join your home network.