I got the same problem. I installed the jpeg-8c lib and it woked for me

You should search in the sabayon-weekly repositorthe entropy database, via cli or using the sulfur program, should see a string "like jpeg-8c branch: 5" or something. The following example is made searchin via cli usin equo:
became root and type
equo search jpeg-8c
should get the following output:
micia wrote:<user@hiscomp># equo search jpeg-8c
>> @@ Cercando...
>> @@ Pacchetto: media-libs/jpeg-8c branch: 5, [sabayonlinux.org]
>> Disponibile: versione: 8c ~ tag: NoTag ~ revisione: 0
>> Installato: versione: 8c ~ tag: NoTag ~ revisione: 0
>> Slot: 0
>> Homepage:
http://jpegclub.org/ >>
http://www.ijg.org/ >> Descrizione: Library to load, handle and manipulate
>> images in the JPEG format
>> Licenza: as-is
>> Keyword: jpeg-8c
>> Trovati: 1 voci
<user@hiscomp> # equo install jpeg-8c
please note the lenguage above is italian
picked up from another topic, to be exact:
http://forum.sabayon.org/viewtopic.php?f=22&t=24729italian forum
hope this helps
hope that will help