Guitar Rig (or other guitar) plugins with Pro Tools

[rballister]

When I have a basic track (drums, other stuff), I create a new audio track and typically add a plugin for my electric guitar (eleven free, guitar rig, etc.) When the track is armed I hear the plugin, when I don't arm the track I still hear the guitar but without the plugin (clean). With the track armed and RECORDING I hear the basic track and the guitar through the plugin just fine. BUT if I just want to practice along with the basic track during PLAYBACK and hear the plugin on the guitar too (guitar track still armed) I no longer hear the plugin! What am I doing wrong? (I'm assuming I'm supposed to be able to hear the plugin when I just practice along with the basic track)
Thanks for any and all help.