[support] javascriots/Ajax calls not working

Hi, I am working on http://www.opensource-it.com , site based on Drupal 6.10 . The site has been migrated from D5 and I've just changed of hosting company. Since these two moves all the javascript or ajax calls do not work anymore: fivestar ratings, node relationship, community tagging... So a problem with Javascript execution, but I can't find. Any clue? Thanks, Denis