`nan` parameters

[VeliBaba]

Hi! Training with PDNN sometimes ends with the nan parameters. Command is as follows:
python run_DNN.py --train-data "train.pfile,partition=2000m,stream=true,random=true" --valid-data "valid.pfile,partition=200m,stream=true,random=true" --nnet-spec "1320:2048:2048:2048:2048:2048:1947" --lrate "D:0.8:0.5:0.1,0.1:6" --dropout-factor 0.2,0.2,0.2,0.2,0.2 --wdir model --kaldi-output-file model/model.dnn --model-save-step 1
What is the problem?

[VeliBaba]

Is there anybody could help me?