Workarounds...

Yesterday I checked why the Forte Agent news reader didn't launch ImageViewer correctly as an external image viewing application.

I found that they don't enclose the filename with "" when passing it to my program so if the filename contained spaces they pass it as multiple arguments. I went ahead and submitted a bug report but after 24h I didn't hear anything but robot talk from them so I went ahead and added a few lines that check for this case - from now on (2.43) - when running ImageViewer from command line or via similar customization possibilities in other programs the issue should be magically resolved by the ImageViewer itself :)

Just don't push it too much - I just add a single space between the arguments - if you want multiple spaces next to each other in a filename please contact the software vendor to add those ""'s... - that's what they should have been doing in the first place ;)