Hey there,
I took a look at the backend Spanish translation file(JoomlaFolder/administrator/language/es-ES.com_easyblog.ini) and found that there are many _QQ_ characters in there. These are probably added by mistake by one of our volunteer translators.
We will try to remove these characters from the Spanish translation files, but this will take time because there are a lot of them. Do you urgently need the Spanish translation to work in the backend?
In the meantime, for your other sites, do not update the Spanish language files until this is resolved.