Under Snow Leopard my web browsers no longer display thumbnails.

Question

Since installing Snow Leopard neither Safari not Firefox display thumbnails on certain web sites. The most notable being Google picture search. Everything works fine except the thumbnails are empty white rectangles. If I click on an empty thumbnail I will get taken to an image which displays fine. The problem is thumbnails and thumbnails only.
I downloaded Googles own Chrome and even it can't display thumbnails on a Google picture search. The problem exists also on many other picture sites such as Getty images, but not, for example, on Wikemedia. It happens in all browsers - all of which are completely up to date as is my OS X 10.6.2. My video cards and monitors are all Standard Mac issue from Apple and the drivers supplied by Apple as part of the OS.
In all this confusion the one thing that is absolutely 100% certain is that the problem started from the moment I first powered up Snow Leopard. Of that there is NO doubt. Before then there was never any problem. I am a graphics professional and constantly need to picture search. For the time being I have had to dust off my old G4 and use it as a picture search machine and then network the downloads across to the Mac Pro. That is hardly satisfactory.
Has anyone any suggestions for this bizarre problem? I have done a mass of web search and have found no reference to anything similar.
Getting rather desperate after months of this ...... :o((

Answer 1

Well lepkitty I can report success. My browser is now thumb-nailing faster than ever before.
Problem solved!! You get a gold star!!
In case others with the same problem stumble on this thread here is the solution. I am no techie so It will be simple .......
Problem:
Safari, or any other OS X browser doesn't thumbnail Google (and many other) picture searches but hangs forever loading the thumbnails leaving empty white rectangles on the screen. Google maps don't zoom, pan or update. The problem is unique to Snow Leopard.
Cause:
When OS X and Safari (or other OS X browsers) perform certain operations, of which picture searching is one, they speed things up my making multiple simultaneous connections to the host. Rather than loading the thumbnail images one by one they will make multiple connections, to say Google image, and pull down multiple thumbnails simultaneously. Leopard makes up to eight simultaneous connections at a time. Snow Leopard, however, can make as many as sixteen.
This where the trouble starts. Many router's firewalls interpret too many simultaneous requests as a "SYN flood" (This is a form of malicious attack using multiple simultaneous connections. If you really need to know - more here http://en.wikipedia.org/wiki/SYN_flood) It seems quite a lot router's firewalls set the simultaneous connection threshold at 10. My Phillips did and Belkins do too. Any attempt to create more connections than this will be treated as malicious and will be blocked by the router.
Solution:
The solution is to change your router's firewall settings. Every router is different so these directions are rather generic. The precise menus, and wording will change from one to another but, trust me, I am no techie, it's really not difficult .... this isn't going to be rocket science ......
Here is what you do:
You access your router by entering "http://192.168.1.1" in your browsers address box. You will be asked for a user name and password. You should find the default setting for these in your router's manual. (On most it is "admin","admin")
Once in your router's menu you need to look for firewall settings. You may need to look for "Advanced" settings first and then look for "Firewall".
Once you have found the firewall menu you need to look for "SPI and Anti-DOS" (On my router it's inside a menu called "Intrusion Detection")
On the SPI Anti-Dos page you should find a list of options that you can set.
Among these should be the option to change the number of simultaneous connections. On my router it is called "Maximum incomplete TCP/UDP sessions number from same host". It will probably be set to 10. Raise this to 20 and then click OK, Save, Confirm or whatever your router's menu asks for, to confirm and save the new setting.
That's it! Done and dusted. This has not only fixed the problem on my browser but it has given a real and noticeable boost to all my browsing.
So let's hope the earth moves for you too ..... ;o))
... and a huge vote of thanks to lepkitty for pointing me at this.
If you want to know more about this in greater technical depth then follow the link provided by her earlier in this thread.