It sounds like you've recorded at a sampling rate of 88.2 or 96 kHz and it is somehow being burned to 44.1 kHz without actually being downsampled before.
Try setting iTunes' import preferences (iTunes --> Preferences --> Advanced --> Import) to "AIFF encoder".
Then click on the track, and go to "Advanced" menu --> Convert selection to AIFF. This should convert the track to 44.1 kHz, 16 bit - audio CD format.
Try burning the converted track and report back.