Problem with Write Model Operator

Hi, i have a simple process
Read csv-> Optimize(a neural net)->write parameter
                                                  ->write performance
                                                  ->write model

I don't understand why but (and this is happen again) i have this message of error:
Oct 6, 2011 1:29:22 PM SEVERE: Process failed: No data was deliverd at port Write Model.input (connected).
Oct 6, 2011 1:29:22 PM SEVERE: Here:          Process[1] (Process)
          subprocess 'Main Process'
            +- Read CSV (2)[1] (Read CSV)
            +- Optimize Neural[1] (Optimize Parameters (Evolutionary))
          subprocess 'Optimization Process'
            |    +- Read CSV SVMX (2)[114] (Read CSV)
            |    +- Neural Net[114] (Neural Net)
            |    +- Apply Model SVMX (2)[114] (Apply Model)
            |    +- Performance (2)[114] (Performance (Classification))
      ==>  +- Write Model[1] (Write Model)
            +- Write Performance (2)[0] (Write Performance)
            +- Write Parameters (2)[0] (Write Parameters)


Everyone can help me?

Regards

Nello