REPOST: Duplicate entries in Groups

[Streaky]

Hi,

Since upgrading to Messenger 6, I've noticed that a couple of my contacts
appear multiple groups; for example Friends and Other Contacts.

I can't move from the Other Contacts back into Friends because Messenger
thinks they are already there. But if I delete them from Other Contacts they
also disappear from Friends.

Any idea what's going on?

Thanks.

S