This error refers to a problem creating the .flp file that the software writes to. This can be caused by the directory you are saving to not having write permissions. Please try saving the file in another location, for example My Documents.
You may also want to try running the RegFiles.vbs file located in the software program folder, by default these are:
ActivPrimary: C:\Program Files\ACTIV Software\ACTIVprimary
ActivStudio: C:\Program Files\ACTIV Software\ACTIVstudio
Please note, support for ActivStudio and ActivPrimary was withdrawn in December 2011.