The CUI file is under C:\Program Files\Autodesk\MDT 2007\Acadm for XP system.
I have zipped a CUI file for your reference. Maybe you can try whether the issue is there or not.
I am putting the CUI file into C:\Program Files\Autodesk\Acadm 2007\Acadm\ and starting autocad. I go to menuload and load it, but when I try to specify it in ._options under main cusomiazation file, the file size changes from 1.8MB to 2KB and it creates a acdm.cui.bak. The menus aren't fully loading, and I really don't understand why.
Ok, here is an update. I finally got the CUI to load using menuload and the size is no loger changing, but the problem is no matter what cui file I tell it to open, it says they are all invalid. I have tried custom ones, the one you sent, ones copied from working machines running ACM 2007 and it says all of them are invalid.