Are you using the exact same code as in the tut? if so, it doesn't crash on the g_pIGameConsole->IsShown() right above it? if it doesn't crash on that then they've probably modified the vtable layout or Show needs a boolean as argument now to indicate wether to show or hide it.
If it's not that then g_pIGameConsole is probably(most likely) a NULL pointer, probably caused by TF2 not using GameConsole003 anymore, which means the VTable layout probably changed as well. Open up gameui.dll in ollydbg and do a string scan for GameConsole, see what number they use and try to use that with your code.