You probably upgraded from an older version and did not update the DB. I'm saying this because the same happened to me. Can't tell you exactly which versions, sry. But the problem is this:
Some varchar column lengths are/were too short (255) which causes serialized object from the Facebook graph to be truncated. And they can't be unserialized anymore (technically they are corrupted).
Easy fix: rerun the install SQL script. (
Your existing data will be dropped!!!) Check your install package: com_jofacebookgallery_jl_3.x_unzipped/admin/sql/install.sql
Alternatively, if you did not upgrade or don't have the latest version, manually go through the tables and change the problematic columns from varchar to text. I haven't taken the time to found out which exactly. At least #__jofbpt_photo.source. Quick search in the install script for all text columns yields this:
CREATE TABLE `#__jofbpt_albums` (
`fbpage` text NOT NULL,
`from` text NOT NULL,
`description` text NOT NULL,
`params` text NOT NULL,
CREATE TABLE `#__jofbpt_category` (
`description` text NOT NULL,
`fbpage` text NOT NULL,
`params` text NOT NULL,
CREATE TABLE `#__jofbpt_photo` (
`from` text NOT NULL,
`tags` text NOT NULL,
`source` text NOT NULL,
`images` text NOT NULL,
`params` text NOT NULL,
CREATE TABLE `#__jofbpt_settings` (
`value` longtext,
