When XST duplicates registers by default, it adds a "_n" to the name of the original register. In ISE 8.1i, this does not occur for the first register, which is duplicated, i.e. instead of "e", "e_1", "e_2", "e_3" .
This is a problem with XST when the RTLViewer option is set to "Yes". To work around this issue, set the "Generate RTL Schematic" in ISE to "No". Refer to the XST User Guide or ISE Help for more information on how to set this option. These documents can be accessed at:
The issue is fixed in ISE 8.2i.