Hello Rama,

I am not sure what the issue is with that particular runtime version for the toolbox utility.  If you would like you could submit a support request for this and place it under general asp.net.  Then just explain the issue. 

However, we can get you up and running a little faster.  Right click in the toolbox and select Add Tab.  Then put NetAdvantage 10.3 ASP.Net CLR35 or whatever version you may need.  Then go to C:\Program Files\Infragistics\NetAdvantage 2010.3\ASP.NET\CLR3.5\Bin and select all the .dll items in there.  Then just drag and drop them into the tab that was created in the area that says "There are no usable controls in this group.  Drag an item onto this text to add it to the toolbox.  This should be all you have to do and is usually the method I use to add controls to the toolbox.

Furthermore, you can also create the tab like above and then right click and then choose Items.  Then just select all the controls that you want to use.  This way takes a little while, but they will definately get in there.