As I still have this problem, I re-read this thread and realized something about what you said.
You said, "In my local 6.2s, it I get the 'This member has been deleted' error, not the one you've noted."
However, if you look at my screen shot, you will notice there should be 9 messages in the 'sent' area but only 2 are displayed before the error. The rest are unreachable.
Now I knew this, since they're my private messages. I wonder if you realized this as well.
As you said, you get a different error message. Do you also have unreachable messages after the one with the error message? Is your error in the 'To' column, does it replace the whole message, or does it wipe out everything below it like my error? If case #2 or #3, how do you access the message to delete it or even read it?
Your message may be different, but can you really consider the problem fixed in 6.2?