FAT32 file system does not support any permissions. If you right click on a directory on a FAT32 partition and choose Properties, there is no tab Security. If you see a Security tab for the directory containing the UCm configuration files, the drive is formatted with NTFS. You can right click also on the root of the drive, choose Properties and see on tab General the file system of the drive.
I logged with Process Monitor the file accesses on this file by UC Prof. v18.104.22.1687 if it is not present and on a Windows 7 x64 computer, see the attached CSV file (deleted later). It is interesting to see that UC writes and reads the file several times. It does this also if the file already exists on startup. Very strange. I will report this to IDM support by email as I don't see any reason to read and especially to write the menu profile file if already present and is up-to-date several times during startup.