I recent excitedly upgrade to OS X 10.9 Mavericks. One of the biggest problems is the MPlayerX crashed on Mavericks.
Thanks to its open-source, I checked out the source.
So, the problem is that a value was used before it was initialized, and it was divided as zero. It’s the time slider’s max value, being used to calculate the knob.
The patch is here, also I committed some possible fixes in the repository.
Update The author has updated it, please download it at MPlayerX.org.