That does happen from time to time. The usual fix is bring up the AHIII uploader (currently ver 3, patch 10) and browse to the file, fill in log id etc, but leave upload mission to host unchecked, then click OK. It will create a .res like the build res command in the editor. Close those windows and then try uploading again. Most of the time this works. If not, open the Mission in the editor, make some small change, save it, build res and try uploading again. On rare occasion, I have just had to start from scratch on the mission. One of the mysteries of life in AH. Post your .mis file if you cannot get it to work and I will see if I have the same luck.