Hi Hatif,
Based on the list of Hotfixes, you should be up-to-date, unless I am missing one. You may want to go ahead and open a Symantec Support Team Case on this issue.
You mentioned that you added a new MSCS Cluster node to an existing 6 node cluster. Have you attempted to manually import / deport the Disk Group(s) on the newly added cluster node outside MSCS Clustering? I would recommend this in an attempt to try to isolate the issue. If the Disk Group(s) can be imported / deported manually using the Veritas Enterprise Administrator (VEA), you may simply try to reinstall the Microsoft Clustering Option (if is not already installed, install it) using the Symantec Product Installer, accessed from the Add/Remove Programs list when selecting Change on (Server Components).
