Works just fine with IE9 for all my systems.  Since it isn't working for you, I might recommend: Have you rebooted?  Are the DSM_ services running?
Just rebuilt a server and inadvertently installed IE9, now cannot open Server Administrator.  Accepts no login id's just presents a blanks screen. Have java and activeX and all that enabled within the web browser, there is literally no security in place. Windows 2008 R2 Standard Latest version of OMSA.   Any advice?   Thanks, KBeau
OMSA not compatible with IE9?