"Add to dictionary" grayed out in Office 2007

I've just started using Office 2k7 and I've been having problems with
the CUSTOM.DIC that I imported from my old Office 2000 installation.

First of all, it didn't like that it was ANSI encoded, so I changed it
to Unicode.

Then, whenever I was doing a spellcheck in either Word or Outlook, the
option to "Add To Dictionary" was grayed out. Some light googling
revealed that this can happen if either a) the file is corrupt (it
wasn't), or b) the file was read only (it wasn't) or, c) the folder
containing the file was read only (it was). As the folder was C:\Users
\MyUserName\AppData\Roaming\Microsoft\Uproof and therefore a System
folder, I couldn't change the properties of the folder. When I moved
CUSTOM.DIC to a new folder which was not read only, it all worked
fine.

So, is my only option to move the CUSTOM.DIC to a folder outside the
Users tree, or is there some other way of setting the properties on
the Uproof folder that I just don't get? Why would the application
place the dictionary in a location that is by default read-only, thus
clobbering the utility?

Thanks

Edward