When I install One Page Profile it shows this error.

# warning: Missing argument 2 for user_category_load() in /var/www/drupal/modules/user/user.module on line 1155.
# warning: Missing argument 3 for user_category_load() in /var/www/drupal/modules/user/user.module on line 1155.

I found a similar issue here for Account Profile and this might be also the conflict with Me Alias module. When I disable either One Page Profile or Me Alias module the error is gone.

This might be also relevant to the issue.