Registry error possible, because secondary launch for file2 searches the running Dia (Portable) process. When Dia Portable isn't running already, it can't find it and you get the error.
(I think Xenon uses this way if you associate file extensions with programs).
How are you firing it up?
Do you use the PortableApps.com menu, the commandline or other programs?
This message could appear if you use the commandline or a file manager (like Xenon) and open multiple files.
The above should be fine.
Registry error possible, because secondary launch for file2 searches the running Dia (Portable) process. When Dia Portable isn't running already, it can't find it and you get the error.
(I think Xenon uses this way if you associate file extensions with programs).