Assign Group Ringtones

Hey, I just got my Blackberry 8700c and I upgraded the OS to 4.2.1 and whenever I attempt to assign a ringtone to a group, I get the following error:
"Uncaught exception: java.lang.ClassCastException"

What does this mean and is there any way I can get around it without having to assign a ringtone to every single contact?

Please help ASAP!

Thanks,
Wesley

hey... how did you manage to assign ringtones to groups? Does it only happen on the OS that you have upgraded to? or is there some software that allows us to do this?