What OS are you trying to export to?
Have you checked you don't have a Anti-Virus sofware thats stopping the creation of the files?
Don't worry. There's no virus's in RPG In A Box but it can be quite common for software that outputs files to be blocked by "over-protective" AV.
That would be my first suggestion as its quite clear from the error: it didn't export the .PCK properly, or it did, but it was subsequently removed...possibly in the AV vault/Quarantine if it has such a thing.
Might be worth checking.
