[5 files found, can't recover]

Yes, I'm running the wizard.  Would you suggest I don't?  Actually the message that Recuva had found 5 files showed up as soon as the deep scan began, which is why I was initially optimistic.  

[5 files found, can't recover]

I did a quick scan for some audio files that were on my SD card.  Recuva didn't find anything, but suggested I do a deep scan.  While that was running (it took 13 hours) the dialog says that it had found 5 files which is about the same as I had lost.  When I came back to the computer following the scan Recuva told me that because of filters the 5 files were not recovered.  Does anyone know what these filters are or what this message means?