Connection Problem over wi-fi (PocketCloud Explorer Pro)

Hi to all,
I have a problem connecting my mobile to pc using wi-fi.
If I use 3g all work perfectly, but if I switch on wi-fi on the mobile, then all the pc in the list become gray and if I tap them i receive message: "The remote machine you are trying to connect to is offline and unavailable", then if I switch off the wi-fi all computer icons become blu and I can connect to them again.

Have someone the same problem?