the game worked right away
the only way I could reproduce what you got is if the img file was not there, did you run the Wild Arms [NTSC-U] [SCUS-94608].img.ecm file through unecm
that will give you the Wild Arms [NTSC-U] [SCUS-94608].img file?
renaming the files would have the same effect as the file not being there
ECM + APE guide APE is sometimes used for games with CDDA this game does not have CDDA so you don't need to read the bits about APE
I also checked out the file itself to make sure it wasn't corrupt in any way but the crc checks with the information help at redump.org
http://redump.org/disc/170/