Using Windows XP, Traditional Chinese version, Locale set to Traditional Chinese (Taiwan).
Its not possible to open RMVB files that have Chinese in their name, example: (just copy/paste this into a file name): 小籠饅頭.rmvb
Renaming them to english is a working workaround.
SMplayer version 0.6.7 (SVN r2831)
2009-09-11 02:05:14 UTC in SMPlayer