[NgdBuild 1037] The logic for imported Partition using previous implementation has been modified. This situation can occur when the source for the Partition was modified but the Partition was not re-implemented and exported. You must re-implement and export the Partition before it can be imported into this design.

This error is soooo obscure it is crazy.

All you have to do is close and reopen the synthesized design view:

http://www.xilinx.com/support/answers/41889.htm