Apologies if this is already known, but it is such a nasty bug I thought I had better raise it.
Using yesterdays Cooker I used MCC to add an NFS mount point. The detection of remote shares and the mounting worked fine. Only trouble is when it added the entry to /etc/fstab it also deleted the first line of the table which happened to be my root mount point. Nasty! I have replicated the problem. It has now done it twice in succession. Thanks derek