Microsoft has re-released a bulletin, or rather published an update to an existing bulletin, which originally only had a risk of privilege elevation.  The latest revision of Knowledge Base article 920958 outlines problems that *may* occur with the installation of MS06-049.  According to MS "After you install security update 920958 (MS06-049) on a computer that is using NTFS file system compression, compressed files that are larger than 4 kilobytes may be corrupted when you create or update the files."  We here at ISC now have confirmation of the problem with a reader submitting that yes, indeed, it does exist.  MS has also published a fix for this in KB 925308 in case "you are severely affected".  IMHO you're either affected or you're not and would want to take steps accordingly.