Same here !
Domino 6.5.4 FP1
Sametime 6.5.1 Fix1
IExplorer 6 .0.2800.1106
Exiting Meeting Room or Test your audio/video tools page
Switched to MSJava on IE (Internet Options..advanced), also receive the error.
I'll try different combinations/versions of JVM (and Firefox as well)...If anything comes up I'll post it here.