unsupported attr type = LONGARRAY

Dear CMDBuild-Team,

I’m Using Openmaint in current version - thanks for providing this powerful app.
When I try to add or change functions for charts (i.e. in Dashboards) I get error java.lang.NullPointerException: unsupported attr type = LONGARRAY.
No function can be selected from dropdown-list or added by typing the name into data source field.
Checked this also with an unmodified readytouse instance: the error does not occur here.
What could be the solution?

Thanks in advance.