I followed the instructions, rebooted and as I suspected there was no Flash available to play browser video content. So I downloaded flash, ran the install program but same issues emerged. Firefox immediately displays a flash crash notice. But to my surprise some video will play. Britian's got talent plays. But most other content does not. Same for Safari, it shows a 'plug-in failure' notice where most video should appear. Occasionally, Safari will play a youtube video but not many.
I am still in limbo as to what is the source of the problem and how best to tackle the issue.
Here is a crash report generated by Safari when trying to open wsj.com. I can include the full report if desired.
Process: WebProcess  Path: /System/Library/StagedFrameworks/Safari/WebKit2.framework/WebProcess.app/Content s/MacOS/WebProcess Identifier: com.apple.WebProcess Version: 7534.55 (7534.55.3) Build Info: WebKit2-7534055003000000~1 Code Type: X86-64 (Native)
Parent Process: Safari 
Date/Time: 2012-04-24 22:53:20.373 -0400 OS Version: Mac OS X 10.7.3 (11D50)
Report Version: 9
Interval Since Last Report: 101790 sec Crashes Since Last Report: 139
Per-App Interval Since Last Report: 59221 sec
Per-App Crashes Since Last Report: 4
Anonymous UUID: 81A6BEC2-E947-4A28-B18B-15FE9ABF5C4D
Crashed Thread: 0 Dispatch queue: CA::CG::Queue
Exception Type: EXC_BAD_INSTRUCTION (SIGILL)
Exception Codes: 0x0000000000000001, 0x0000000000000000
Application Specific Information:
objc: garbage collection is OFF
Thread 0 Crashed:: Dispatch queue: CA::CG::Queue
I have removed all the non-essential plugins EXCEPT for 'Facebook Video Calling Plugin'. Even though it is not in the internet plug-in folder nor in the library/applications support folder, the bugger continues to show up as an installed plugin. In firefox it has been disabled.
Yet neither Safari or Firefox is cooperating. Both display the flash crash text. Only on ocassion can will a youtube video play. No rhyme or reason.
In addition to the Facebook video call plugin which is disabled, the only other plugins installed are quicktime, iphotophotocast, java, webkit built in pdf (only showing in Safari, not Firefox) which doesn't have a file name associated with it, and shockwave.
Please read this whole message before doing anything.
This procedure is a test, not a solution. Don’t be disappointed when you find that nothing has changed after you complete it.
The purpose of this step is to determine whether the problem is localized to your user account.
Enable guest logins and log in as Guest. For instructions, launch the System Preferences application, select Help from the menu bar, and enter “Set up a guest account” (without the quotes) in the search box.
While logged in as Guest, you won’t have access to any of your personal files or settings. Applications will behave as if you were running them for the first time. Don’t be alarmed by this; it’s normal. If you need any passwords or other personal data in order to complete the test, memorize, print, or write them down before you begin.
Test while logged in as Guest. Same problem(s)?
After testing, log out of the guest account and, in your own account, disable it if you wish. Any files you created in the guest account will be deleted automatically when you log out of it.
Note: If you’ve activated “Find My Mac” or FileVault in Mac OS X 10.7 or later, then you can’t enable the Guest account. Create a new account in which to test, and delete it, including its home folder, after testing.
The purpose of this step is to determine whether the problem is caused by third-party system modifications that load automatically at startup or login.
Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards. Boot in safe mode and log in to the account with the problem. The instructions provided by Apple are as follows:
- Be sure your Mac is shut down.
- Press the power button.
- Immediately after you hear the startup tone, hold the Shift key. The Shift key should be held as soon as possible after the startup tone, but not before the tone.
- Release the Shift key when you see the gray Apple icon and the progress indicator (looks like a spinning gear).
Safe mode is much slower to boot and run than normal, and some things won’t work at all, including wireless networking on certain Macs.
The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
Note: If FileVault is enabled under Mac OS X 10.7 or later, you can’t boot in safe mode.
I'm not sure whether Flash works at all in safe mode, but test. Same problem(s)?
After testing, reboot as usual (i.e., not in safe mode) and test again. Post the results.
I followed the instructions and experienced only slight improvement. Under safe mode, both personal and guest accounts displayed similar behavior. Videos on Vimeo, WSJ, and Youtube would start but only play for 2 seconds and then freeze. The behavior is true regardless which browser I used. Flash does run in safe mode and did not crash. So we are making progress.