Have you tried this in another browser, have you rebooted, and have you possibly upgraded Java to the latest just to be on the safe side? I'm using iDrac sessions on both Windows and Mac with no issues.
I've tried multiple browsers.
I've tried multiple machines.
I had this problem before and fixed it some how.
I just can't remember how.
Go to JAVA setting ("configure java") and delete temporary files
This should work ... it worked for me
This occurs when there is already jp2launcher is running. In task manager, find jp2launcher.exe and kill this process and try again.
I hope this helps.