What version of Nero do you have? Is it the NEro 188.8.131.52, or did you upgrade to the Nero 184.108.40.206?
For my tests, I am using Nero 220.127.116.11, as I assumed you would have this, as Nero 18.104.22.168 was only posted on the website yesterday.
Are you only using Nero SoundTrax for the ability to do Crossfades? Becuase if that is all you want to do, there is a much easier way to accomplish this than to go through Nero SoundTrax. You can just launch Nero Express, select the option Music->Audio CD and then add all your audio files. Then Select all your audio files and click on the Properties button on the right. And then at the bottom of the 'Audio Track Properties' window, you will see the option for Cross Fade. Just check the box, and then enter in how much of a crossfade you want in seconds.
As for SoundTrax, not working when burning, I'm at a loss as I can not duplicate this issue, and if it were simply a software feature not working, then it should be across the board and easily duplicated.
What model recorder do you have? Can you send me a copy of the log file from the write attempt with SoundTrax at firstname.lastname@example.org