@hnla: Errr. You are definitely right. It was my late night coding that prevented code stripping when editing group description that stopped the upgrade.php script to function. Everything is working now. I just commented out my function and everything worked like a charm again. Thanks for sorting this out for me!
Solution: In database table “wp_bp_xprofile_data”, I found three multiple rows that was a duplication of the user that was displayed multiple times in the group member section. I have deleted all the rows that was a duplication. Let us hope that it won’t be any problems because of that.