Ajax fails to render admin controls using ie8 on nopCommerce v1.6

All the pages below refuse to render using IE8, but work fine with Firefox 3.6.3. The page returns the top half of the page down to the border below the page title and then gets stuck waiting...

ProductDetails.aspx, CategoryDetails.aspx, ManufacturerDetails.aspx, CustomerDetails.aspx etc...

I have tried everything I can think of;

Reinstall ASP.NET 3.5 SP1
Download AJAX Control Toolkit v40412
Add <xhtmlConformance mode="Transitional" /> to webconfig
Clear Cache
Disable Firewall

No Errors are raised and Trace returns nothing unusual

I'm using a development environment: win 7 pro, vs 2008 express

I have seen other people on this forum have had this issue but there's not many solutions

Any Ideas?

In IE8 you have developer tools. Press F12 to see it. There (on the top of this developer panel) you can play with Document Mode and Browser Mode. Try to change it and refresh page. Tell me what happens

Browser Mode: IE7 - Document Mode: IE7 Standards (No Change)
Browser Mode: IE7 - Document Mode: Quirks (No Change)
Browser Mode: IE8 - Document Mode: IE8 Standards (No Change)
Browser Mode: IE8 - Document Mode: IE7 Standards (No Change)
Browser Mode: IE8 - Document Mode: IE7 Standards (No Change)
Browser Mode: IE8 - Document Mode: Quirks (No Change)
Browser Mode: IE8 Compatibility Mode - Document Mode: IE7 Standards (No Change)
Browser Mode: IE8 Compatibility Mode - Document Mode: IE8 Standards (No Change)
Browser Mode: IE8 Compatibility Mode - Document Mode: Quirks  (No Change)

Interestingly the Demo admin site does work after a long delay the page appears. 10 seconds approx. This delay is worse with FireFox 20 seconds approx.

Do you want the HTML Output source?

No idea

Thanks for your time LevGe

SOLVED

Full Reset of IE8 to default

Tools > Internet Options > Advanced > Reset...

Found a solution here
Nopcommerce 1.6

http://jugaadtech.in/8/ajax-toolkit-tabs-problem-in-nopcommerce

Hope it may help somebody ;-)