Q: Why does my entire system freeze when I watch YouTube after Lion install?

I have the same problem on 27 " iMac model12,2 i7 4 Go SMC 1.72f1 running Mac OS X 10.7 (11A511).

Yes, this is the work around that I am also using until Apple come up with a 'fix'.

ok I have been back to SL on exernal drive. 0 problems in 6 days or so.

same problem

1.  new 2011 27" imac

2.  Start youtube video playback

3.  Computer freezes, only move mouse cursor

Just like to give an update.

My 2010 MacBook Pro Core i5 had been having these problems, but hasn't happened in a while after a clean install.

I had been having these same sort of lockups during restarts. Learned that was related to the automated graphics switching. Turned off automatic graphics switching, haven't had a problem since.

Related or not? Worth a try I suppose.

This issue is also being discussed here (the title says 27" but it's happening on all new models)

https://discussions.apple.com/thread/3194165

Not related as this is a Thread for Mid 2011 iMacs not MacBook Pros.  Besides iMacs are always plugged in. 

Yep and the same fix applies.  Set the iMac to Never Sleep in the Engery Prefrences and wait for Apple to update and fix the problem or downgrade to Snow Leopard. 

silly question, but is there any harm to the computer itself if its always on and never goes to sleep?  or just you electric bill?

thanks

Your hard drives and display will still sleep provided they are set to do that in the energy saver preferences. The processors etc just stay powered up. Difference in power bill would be hard to detect.

but leaving the processors powered up for days, weeks, etc does no harmful things to the computer?

Mid 2011 27" iMac, i7, 16GB I had a freeze on a Vimeo video this morning thru a link on Facebook. But if I watch any videos on my second monitor I am fine.

Just waiting for a fix.

Same issue here, tremendous pain for daily usage.

For everyone with recent (2011 / mid 2011) iMacs with AMD Radeon HD 6970M graphics card can you respond to my question (link to thread below) about RAM on your graphics card.

https://discussions.apple.com/message/15837032#15837032

If in fact it is related to added video card RAM it will be good to have responses in one thread.

Same issue here.

New IMac, worked fine for the couple weeks before I put Lion on it.  Now freezes whenever I watch online video, from various services (or using app store players).  This has happened to me about a dozen times now, I've given up trying to watch video on my computer anymore.

Don't know how they will gather 'crash report' data on it since I've never had the system acknowledge a crash.  It just freezes and you have to hard power off and restart.  It's never posted anything about a crash report to me when restarting.