i got the error above so i checked the contents of the cue file.
Here it is.

FILE "Samurai Taisen - Track 01.iso" BINARY
TRACK 01 MODE1/2048
INDEX 01 00:00:00
FILE "Samurai Taisen - Track 02.mp3" MP3
PREGAP 00:03:00
INDEX 01 00:00:00

i was able to mount the cue extension file by replacing 'MP3' on the end of line 4 with 'BINARY' but the program didnt work well(irritating sound). Is there a way to get this thing work right?