A case has been seen where MAP failed with the error:
ERROR:PhysDesignRules:817 - The connectivity for pin
<registerClockHostReadToReshold(0)> of block
<myWindow/myHookedUpLabVIEWThing/n_297624576> is illegal. A child signal
cannot exist for a pin of a leaf block.
This failure was caused by the existence of empty hierarchical blocks in the logical design.
This problem is scheduled to be fixed in version 8.2i. Meanwhile, the problem can be avoided by disabling KEEP HIERARCHY with the MAP switch "-ignore_keep_hierarchy" or by removing any "empty" hierarchical blocks from the design.