As you mentioned the circuit is 10mb ethernet. Is it half-duplex or full, if it is full-duplex try to config 3560 or 6500 interface to 10mb full-duplex.
I think this is more physical link problem than config erorrs, try to make sure interfaces are up even ports on sw1 and sw2 is configed to access mode port in same vlan then config these ports to trunk mode.try to use diff cables to test (straight, c...