I tried to reproduce this with the current CVS and "it worked for me".

I added a due_date and timelog per customizing.txt, created an issue with a timelog and due_date and then clicked "Make a copy".

The copied issued didn't copy the timelog -- just the due_date.

If you could post step-by-step instructions of how to reproduce this, that would be great. If you could do it on roundup 1.3.3 or CVS it would be even greater :)