TIP:
When you upgrade vB versions, the installxx.php files will automatically install the new upgraded templates for you.
HOWEVER, it will NOT replace templates you have modified.
This is why you had that problem - you were probably using a vB 2.2.9 showgroups template, with a 2.3.0 showgroups.php file.
The showgroups templates were announced to have undergone major changes in the latest upgrade. After upgrading, always revert templates to default, as the default templates are now the newest versions - then reapply the hacks.