Blender won't read multilayer EXR after 125 frames

Hello, I am having problems reading multilayer EXR files in the compositor. They are 32bit PIZ.

I can load an image sequence and after 125 frames Blender will stop reading the layers but it will still read the first/top layer. I can open up each frame as a single still image and Blender will read it no problem.

Tried this on 2.72b and 2.73 win7 enterprise x64. The EXR files were created by Mentalray in Maya via render passes. The sequence and Blender project are set at 1-530 frames.