Crashing with 256x64 from FlexDMD via VPX standalone

[jsm174]

This issue was reported here: vpinball/vpinball#1094

I went in and ran the debugger with all the libraries compiled in debug mode. It seems to be crashing when locking the mutex.

The width and height are correct at 256x64

Here are the stack / vars from some more context:

[francisdb]

Should probably be moved to https://github.com/PPUC/libzedmd ?