I have seen those characters when the nios2-terminal gets into a corrupt state. Try deleting the jtagserver and nios2-terminal processes with Windows Task Manager (via ctrl-alt-del), after having exited the IDE and any Nios II command shells (a reboot wouldn't hurt either). You can also try using the pre-built multiprocessor hardware design to rule out any SOPC Builder design errors, available on the Nios II Multiprocessor Design Example web page, at http://www/support/examples/nios2/exm-multi-nios2-hardware.html (you will need a 2c35 or 2s60 Nios Development board to try the prebuilt reference designs).