Have already downloaded 4.2.3 and installed Xmarks NEW from Xmarks website. Running Firefox 25.0.1 on Mac OS 10.6.8. Ran Xmarks settings repeatedly. Xmarks syncs on MacBook Pro with 3 tabs. Xmarks syncs on MacPro Tower with 34 tabs. Unable to get Xmarks on MacBook Pro to Synch with 34 Tabs on MacPro Tower, despite being told that Xmarks synched correctly with the Server. Apparently, Xmarks Server has two addresses that it is saving too. My problem is only having one address, the 34 tabs on the MacPro Tower. I tried setting the Macpro Tower computer name in Xmarks Setup on the MacBook Pro, but it did not solve the problem. XMarks worked incredibly well when I was running OS10.5.8 on both machines. Problem started when I undated from OS10.5.8 to OS10.6.8. How do I get both computers to synch with the 34 tabs already synced on the MacPro Tower?