I too have just been starting to get the blue question marks. I've had my Macbook Pro, Safari 5.1.5 for about 3 month. I called tech support at Apple and they seemed to think it was one of two things. They had me download a new version of Flash which initially seemed to do the trick, but then later I was back to the blue question marks again. Since it's Easter today they are not open. Ill call back on Monday and find out what the second thing was that they thought it could be. I never had this problem until just recently. It shows up on Utube and Yahoo as well as other sites. No problem when I use Firefox though. Kinda aggravating isn't it?
I notice that when I reload the page sometimes Ill get the graphics back and sometimes not.
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I reinstalled Flash again and it corrected the problem, but like before it may go back to the blue question marks again. Wonder if Flash is getting corrupted somehow? Interesting though. Also, tried to reinstall Safari 5.1.5 but didn't help. Yes, the plot thickens.
What I've found was that when I reload Flash it corrects the problem, but when I "quit" Safari I get the problem back. Right now Im just minimizing Safari and it seems to be working ok. Is something in Safari corrupting Flash?
Monday: Called Apple. This is what they had me do... Close out all your programs. Hold Option button and under Go, select Library. Find Preferences and double click to open. Look down the list and find com.apple.safari.plist and drag to the trash can. Empty the trash. Restart your computer and open Safari (it will be a little different) Now go to your web site that your getting the ? marks at and see if that take care of the problem. So far so good. Hope it stays now.
Tuesday: Question Marks are back so the above didn't work. Apple says to download a new copy of the Operating System. Mine is Version 10.7.3. Ok I did that and took a couple hours but so far no blue background ? marks. Hoping this will do it but if it got that way once it will probably do it again down the road. Good luck people.
Thursday: The question marks are back. Just loaded up the App Store and half of them are question marks. Going to make one more call then just start using Firefox as its getting aggravating. Over and out!
Friday:4/14/12 Called Apple. Senior Rep went through all kinds of things to try and resolve the problem. Nothing worked, so is handing it over to the Engineers to see if they can figure it out and get back to me.
Monday: 7/2/12 Just checked my App Store and web sites and the blue ? marks are gone. They must have resolved this issue. Thanks Apple!