Abort has nailed it. You have to be very careful about what your diagram APPEARS to show and what the connection configuration really is, because the labels S0/0
etc are simply that - LABELS - they don't necessarily move when you move devices around.
SO although your diagram SEEMS to show that R8 S0/1 is connected to R10 S0/0, in actual fact R8 S0/1 is connected to R9 S0/0. You can see this in your topology if you go to the GNS3 Command console and issue a show run
0809_02_03-WorkSpace Window description.png [ 206.25 KiB | Viewed 3224 times ]
Illustration taken from theGNS3 Network Simulation Guide:
Disclaimer: I am the author of theGNS3 Network Simulation Guide
-a VMware image of Ubuntu with GNS3 and VPCS installed and a collection of exercises/labs