serial port don't work

I was working with Developer Studio and suddenly, when I try to run the aplication, the follow message appear:
“No target detected (no response to AT+WMNS comand)”

The serial port detect a device, but it can’t know who is it because it don´t get response
What are happening??

thanks.

Try just a simple, basic terminal (emulator) like Hyperterminal.

Does the device respond to that?