[popcornmix]

and here is a log of the Pi playing the video then pausing
http://pastebin.com/pb3D9Zys

Code:

10:46:18  19.022640 T:3057111040   ERROR: unable to load:/storage/.xbmc/addons/skin.quartz.test/1080i/DialogSeekBar.xml, Line 0
                                            Failed to open file

I think you need to look very closely at that file and compare it to other files.
Either a permissions issue, the filename/path is wrong or there is something bad in the file (like a syntax error, incorrectly matched brackets or incorrect newlines).

Can you revert that file to the stock Quartz one and see if it loads?