The timing engine creates a timegroup with all of the DLLs in the
design in order to implement path tracing controls. The code needs
to be improved to both check for the possibility that a user has
created a timegroup with the name "DLLS" and to look for a
timegroup already created by the timing tools.
A fix for this problem is included in the 1.5i Service Pack 2. For details
on this Service Pack see http://www.xilinx.com/techdocs/5887.htm