I had the same problem - I "saved as" and then when I went to re-open the file later - an error message saying "THe file provided is not a valid VideoPad project file". THe file was saved several times and it is a .vpj.
It looks like several people are having this problem. is there anything to do to try to salvage the file?
C-Major - when you say "out of memory" - do you mean on MY local computer - or do you mean on the NCH server? I have 8 GB of ram which should be sufficient.
Starting last week I experienced the same "failed" message each time I uploaded. First it as with exporting to Youtube (4k), then when exporting to .mp4.
I purchased directly from NCH - registered - VideoPad professional v.4.58 Windows 10.