My guess (and that's all it is) is the file name isn't matching thetvdb.com listing. I'm making an assumption looking at your log (I can't read the language, so perhaps I've overloooked something) that the series is The Simpsons. I see a folder name of "Os Simpsons", but the file names only contain OS.
Assuming I've got the correct series name, I suggest renaming your files to say "simpsons S6E21.avi". It appears the metadata search function is reading the series name as OS. When I check thetvdb.com for OS or OS SIMPSONS it doesn't match anything. I just checked IMDB and I see The Simpsons is also called Os Simpsons in Brazil and Portugal, so that's probably the correct series. You can use the IMDB ID number in your file name to assist matching the metadata. For The Simpsons, the ID is tt0096697. See this page for an explanation on using the IMDB number:
http://wiki.serviio.org/doku.php?id=imb ... ata_naming