YankeeJim: ScottHope explains the number.
It was funny and I'm sure he was joking, or guessing, as he has previously stated he knows zero about programming.
The issue is with the SQL Message DB Query Schema. It is not recognizing anything over, let's say, 255 or so names . WGT most likely has the table query set to only recognize the first 255 user id's in your friend list. Therefore, anything over that number shows as "user not found" in the message client.
Think of it like a "spam filter" in your email client.
The same holds true for your friends list, OP - anything over 255 and you will not see their "Status" on your friends list table <<<<< on the left.