Exactly the same issue, and no one seems any closer to an answer on this one. I tried just about every image out there, with no success.
I suppose the answer lies somewhere in how network I/O is redirected ..
I'm having the same problem using Ubuntu. When the qemu host in not connected, It works fine (running microcore-3.4 ), and I can see the qemu process started:
# ps -aux | grep qemu
root 4725 9.5 4.6 322852 45496 ? SNl 22:23 0:04 /usr/bin/qemu -name QEMU1 -m 256 /home/marcelo/.gns3/Pix2Qemu/working/QEMU1/FLASH -hdb /home/marcelo/.gns3/Pix2Qemu/working/QEMU1/SWAP -net nic,vlan=0,macaddr=00:aa:00:42:24:00,model=e1000 -serial telnet:127.0.0.1:3000,server,nowait -no-acpi -vnc 127.0.0.1:1 -cdrom /home/marcelo/IOS/microcore-current.iso
But if I connect the host to a router or another device, the qemu process doesn´t start anymore and It doesn't work. I don't know where the problem could be. I tried to connect it directly writing the .net file and starting the topology , but the result is the same.
Any help would very appreciated