I've been having this problem for a while now on my iMac (OSX 10.6.3) where a file would just rename itself into something like "FULLM~20.MKV" after I rename a different file within the same folder. It's occurred in several folders and is really annoying because I don't know what the original filenames are and messes up my organization. I took note of some occurrences below. If I recall correctly, trying to fix the messed up filename sometimes works but it eventually gets messed up again. It's not limited to video files only, I've seen it happen to a jpg at least once. Renaming "✘ Hetalia Axis Powers 33v2 [Webcast].mkv" to "✘ Hetalia Axis Powers 33 [Webcast].mkv" automatically renames "✘ Hetalia Axis Powers 37 [Webcast].mkv" to "_HETA~34.MKV" Renaming "_HETA~34.MKV" to "✘ Hetalia Axis Powers 37 [Webcast].mkv" fails with error message "The name ✘ Hetalia Axis Powers 37 [Webcast].mkv is already taken. Please choose a different name." Renaming "FULLM~20.MKV" to "Fullmetal Alchemist Brotherhood 20.mkv" fails with error message "The name Fullmetal Alchemist Brotherhood 20.mkv is already taken. Please choose a different name." Everything changed back to normal after renaming a few other files within the same folder Renaming "Oha Suta 20100331 [+, Koharu Kusumi].mp4" to "[+] Oha Suta 20100331 [Koharu Kusumi].mp4" automatically renames "Oha Suta 20090526 [Koharu Kusumi].mp4" to "OHASU~16.MP4" I undid that and added another file into the folder called "Ogawa Saki - Oha Star 100521.mp4" and renamed it to "✘ Oha Suta 20100521 [Saki Ogawa].mp4". Doing the same renaming thing above then worked fine. The weirdly named files work fine though.