The above posts are correct. However, your real problem CEP. I'm less and less impressed with CEP the more I hear about it.
I tested this out with n-Track. I created a little beat in fruity loops, and then exported the beat. I opened the exported file in n-Track and made sure that it was correct. Then I changed the beat in fruity, and exported to the same file that n-Track already had open (i left n-Track and Fruity open the whole time of course). I clicked play in n-Track and voila, it played the updated wave, without any intervention. Then I opened the wave in Wavelab and cut out a good hunk of it and hit the save button. I went back to n-Track (which still open) and clicked play; like magic it played the updated file.
If this wasn't possible, it sure would be hard to use external editors in multitracking applications. So my bet is on CEP, since it claims to be both a full purpose editor and a multitracker. In fact, some people use CEP as their editor in other multitracking apps.
n-Track doesn't leave files open. It reads them directly from disk when it draws waveforms, and when you hit play. This is how multitrackers should work. Now if I have a file open in Wavelab and try to export that same file from Fruity, it certainly doesn't work.
Anyway, this all applies if you described your situation properly. You refered to your soundcard several times, and I think the term you're looking for is "multiclient."
Multiclient: the ability for a soundcard's drivers to allow multiple applications to open the soundcard at the same time. In other words, you can click play in two applications and you'll hear the mixed output of both. This is especially handy in applications that lock the soundcard, like n-Track and many audio applications. The Delta has multiclient drivers.
Full-duplex: a soundcard that is able to record and play at the same time.
Multitasking: running more than one application at the same time. Windows of course gives you the power to do this, but as was stated above, you can't have two applications writing to the same file at the same time.
Slackmaster 2000