{{{I did try to use the transfer, but my goal is to return the CUI file to my client with the changes I make. So rather than loading as a partial CUI to my main CUI, I'd already set their custom CUI to be my main CUI, and figured I'd rename the new CUI (the one created by the transfer) to the same name as the old CUI (the one I received from the customer). This might have worked had I not been missing some of the bmp files for their toolbar buttons.}}}
There must be yet another reason why it's read only, because I have no Enterprise CUI (I'd be able to tell by looking in Options>Files>Customization Files>Enterprise Customization Files, right?), and when I look at the CUI file in Windows Explorer, the read-only box is unchecked, and I have full write permission for the folder that houses the CUI file.
Any other ideas?