Certainly a bug of MLT. What's your version of MLT ? 0.44 ? If i had an advice to give you, it's trying the last version 0.4.10, she resolved a lot of problems but not all. They are going to prepare another version for resovling all the bugs that the precedent version have not done. call Yauba but she is not yet ready. For the 0.4.10, you must compile it.