Starting the debugger fails

I tried to use the debugger. I've followed the intructions in the reference manual.

First starting

debug program

.

When I start the Debugger in the IDE, I get the following error message:

An existing debugging session is running. Trying to return Linux to a  known state.

and the Linux reboots.

The output from console

#  nios2-gdb-server listening on port 2342#   accepting gdb connection#   connecting to JTAG debug module#   CPU will be reset on connect#   using MDI port: "sld"#   JTAG cable: "USB-Blaster "#   JTAG device: 1#   JTAG debug module instance: 0#  step: c#   tcp receive failed#   closing gdb connection

I have no other debug session running. So, what may be the problem?? http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/sad.gif