Here's a few ideas:
1)Check the pan on your main monitor bus (where you see the output levels in "console view"). Make sure it is centered. I haven't used Cakewalk in a while, so I'm not sure it even has a pan on the main bus, so I could be way off on this.
2) Try diabling any effects or aux busses you have going and see if the problem persists. Sometimes stereo effects can do strange things.
3) Are you sure that "left" was selected for recording? It almost sounds like "stereo" was selected. "Stereo" would require two mics, one into channel 1, the other in channel 2 (or channels 3/4, 5/6 etc.). So, if you only put one mic into channel one, and selected "stereo 1/2" you recorded in stereo, but with guitar on one side (input one) and dead air recorded on the right side (inpput 2).
To make sure, in your main clips window (where you see the wave forms), double click the waveform. You might see one waveform and one straight horizontal line. This would explain why you lose the track when you pan.
4) It could be a playback problem. One your main monitor bus meters, you should see the outoput meters from both the left and right output channels. Do these meters change when you pan? If not, maybe you just have a bad connection to yone of your monitors.
5) in the Aardvark control panel, check the output meters. Make sure pans are centered. Note what happens to the meters when you pan in Cakewalk. It will help narrow down the possible problems.
Hope one of these helps.