Something recently changed on a development server that disabled the ability for IE to open xml documents.
I resolved it by following these steps:
1. From start menu select run
2. Type ‘regedit’ and press enter. This will bring registry editor.
3. From the regedit menu select Edit and then Find
4. Type “HKEY_CLASSES_ROOT\Mime\Database\Content Type\text/xml” in the ‘Find What’
5. Regedit will find the content that is related to that entry
6. Verify your classid CLSID={48123BC4-99D9-11D1-A6B3-00C04FD91555} ?
7. Verify your Extension=.xml ?
8. Verify your Encoding=hex:08,00,00,00 ?
If all those values are correct, but still not working, do the following:
1. From start menu select run
2. Type ‘regsvr32 msxml3.dll’
3. Click OK on the dialog box.