1. While it is hanging I take a memory dump of the process using

adplus -p <PID for the IExplore.exe process> -hang

2. I open up the dump in windbg and set the symbol path

.sympath SRV*c:\websymbols*http://msdl.microsoft.com/download/symbols
.reload

3. I load up sos.dll from the silverlight directory

.load C:\Program Files (x86)\Microsoft Silverlight\2.0.30523.8\sos

Start Debug:

0:010> ~* e !clrstack

!dumpheap -type Exception

 06307110        1           72 System.Exception

0:010> !dumpheap -mt 06307110    
 Address       MT     Size
 0638d870 06307110       72

0:010> !pe 0638d870