Resource models was renamed from Resource to ResourceModel.
It leads to the bug 2072.
To fix the bug run the script below:
START TRANSACTION;
SET @from = '\\Resource\\';
SET @to = '\\ResourceModel\\';
UPDATE eav_attribute SET attribute_model = REPLACE(attribute_model, @from, @to);
UPDATE eav_attribute SET backend_model = REPLACE(backend_model, @from, @to);
UPDATE eav_attribute SET source_model = REPLACE(source_model, @from, @to);
UPDATE eav_entity_type SET entity_model = REPLACE(entity_model, @from, @to);
UPDATE eav_entity_type SET attribute_model = REPLACE(attribute_model, @from, @to);
UPDATE eav_entity_type SET entity_attribute_collection = REPLACE(entity_attribute_collection, @from, @to);
COMMIT;