Ok its been over a year since ive needed help on converting a file yet i knew this day would come. Heres my problem.

Im trying to convert a 21 min long h264 .mkv file with the program Alltoavi, now i love this program and have used it for aslong as i can remember but with this file it keeps telling me that i have to change the command line before i can convert it. So i followed all the directions about not placing it directly on the HDD and to put it in a folder but it is still giving me the same error and i cant think of a way around it. So if anyone else has had this problem and has conquered it LEMME KNOW HOW!!!! Thanks in advance