Error message

• Notice: unserialize(): Error at offset 4937 of 10468 bytes in DrupalDatabaseCache->prepareItem() (line 449 of /srv/www/www_usracebook_com/includes/cache.inc).
• Warning: Invalid argument supplied for foreach() in field_attach_load() (line 660 of /srv/www/www_usracebook_com/modules/field/field.attach.inc).