I went in to do some minor adjustments in a client's file (MX3000) and blew it. I attempted to export a button from the Alpha file direct into the client's file (as opposed to saving elswhere and then importing it) and now I can't open the client's file. It says MXEditor cannot open it and to check file type. File type is Rce, the same as all other files saved in my editor. What have I done? How can I bring up the file without having to upload from the remote? Any insight?

It sounds like you saved the image file as the same name (and same extension) as your original .rce file (type .jpg or .bmp into the end of the filename and see if the graphic opens) - in any case, I think you've overwritten or original .rce and would have to upload it or re-create it.