Opening .mp4 files using flvplayback component 2.5 in Air 3.2

I've publishing the package using the extended desktop profile and captive runtime.

When I run the published .exe file from a hard disk (either on my local machine or other test machines) it works fine, so I know that I have my code at least partially correct.

I'm accessing the .mp4 files from a subdirectory of the applicationDirectory (eg: app:/video), the file names are read in from a .xml file.

Example structure:

exampleVideoSource = File.applicationDirectory.url+"video/12-16/attacking when in balance/counterattacking 2.mp4"

Is this likely to confuse the FLVplayback component, if so what's the best way to get a working path?

Thanks,

Dan