[Click] dump not created

[Enrico]

Hi, I have another problem.
I use todump/fromdump elements.
If I run this simple configuration:

FromDevice(eth0)->Print(ok)->ToDump(prova);

I look packet's print on video but dump file "prova" is not created! 
Then, if i try the same configuration one day later (as an example) ...
"prova" is created correctly! 

I don't understand this behavior...what do I do?

Sorry for my english...

Enrico