Webpage fails to display unless refresh key is pressed

We had a problem with a webpage in IE8. This was a rather specific problem.
If we tried to open the same webpage in 4 seperate tabs the 4th tab would fail to load the page.
It would display a no content found type error message. However if page refresh is performed the webpage displays correctly.

This problem is related to Sophos and the IE8 Tab process handling.

The workaround we found for this error was to increase our TabProcGrowth figure. We set
our to 10 which meant the page would only fail on the 10th Tab. (plenty enough tabs for users)
The TabProcGrowth Registry key lives here
HKCU\Software\Microsoft\Internet Explorer\Main
[reg_sz] TabProcGrowth = 10

More detail on this registry value and its implecations are detailed in a MSDN Article here
http://blogs.msdn.com/b/askie/archive/2009/03/09/opening-a-new-tab-may-launch-a-new-process-with-internet-explorer-8-0.aspx