I have installed hundreds of seats of Microsoft Online (BPOS) with no issues.
I have a user with a nearly bran new Lenovo M75e desktop with Windows 7 Pro on it.
When I download and install the Microsoft Online single Sign on tool I have no problems. When the tool runs I have the outline and name of the window and nothing else. Inside the window is all clear and I can see the Windows desktop.
Microsoft's answer was to reload the application 10 times.
Th machine is 100% patched up with .Net installed.
I have verified that on an uninstall all the program files are deleted and the registry keys (provided by Microsoft) are removed.