NI Guitar Rig Mobile + GTP 4 help needed

I have the Native Instruments Guitar Rig Mobile USB device. I can use it with the Native Instruments Guitar Rig 4 software in standalone mode, and have no latency. I can either use headphones, or redirect the audio out of the device to line in on the PC and hear it with no latency, and crystal clear. I can record with the built in "Tape Deck" with great results.

When I try to use the guitar rig mobile with Guitar Tracks 4 Pro, I cannot hear the guitar at all in bypass mode, and when I turn on input echoing, I can hear it but there is latency, so playing along with a drum track is not possible, even with latency reduced to the minimum. I cannot hear the guitar through headphones connected to the GRM out, and if I connect the GRM to the line in on the PC while using GTP, I get horrible distortion in the recorded track.

I have tried simply plugging the guitar into the mic input or the line input on the PC via 1/8" mini plug. Both yielded lousy, low level, and distorted results, although I could at least hear the guitar. I notice there is a HUGE difference in the volume levels, between input echo being on and off (on is many times louder).

Why can I not hear the guitar without input echo turned on? I can still record a track, without being able to hear the guitar, and it records correctly, but I hear no sound, until I play back the track. How do I correct this? I attempted to ask tech support this before joining the forum, but the send button takes you to a broken URL, and the FAQ for the Cakewalk USB interface also has a broken URL. Thanks in advance.

Win7 x64, Quad core, 6 Gb RAM, Realtek HD Audio