After Drupal 5.3, Users show up multiple times in 'Whos online'

After Drupal 5.3, Users show up multiple times in 'Whos online'
Running multidomain + singlesignon with 2 subsites. If I visit a subsite, the user is shown as being online twice, after visiting all 3 sites, user is shown being online 3 times.

Any clues to help me out? :(