It seems that Apple may be taking lessons from Microsoft and releasing Operating Systems before they are ready. A few quick searches show that Mountain Lion, the most recent version of OS X, has many weird issues.
More importantly, both Lion and Mountain Lion are having trouble with connecting to IMAP email services, including Google Apps. Again, looking around the web, upgrading to Mountain Lion may break your Gmail/Google Apps connection.
If you have upgraded and are having trouble, feel free to contact us under your support contract. We also welcome inquiries from companies interested in Google Apps support services.