[galaxy-user] Unable to import dataset from history into data library

Dear Galaxy Users, Since I've updated my Galaxy version I'm unable to import any dataset from my history into my data library. It returns a message of e.g. "Invalid item id (1464) specified". I then did a complete new test installation to make sure that this problem wasn't because of the update. But the error still remains. I've included a screen shot in which the error is reported. When I queried the database the dataset id does exist in the history_dataset_association table. I went through the paster.log file and found the following warning message: Unknown library item type: <class 'galaxy.model. HistoryDatasetAssociation'>. Can it be that this class is not loaded or found? Is anyone experiencing the same problem? Thanks,