Jim,
Is there any sort of error number or additional text that is associated with that error? Checking the "Disconnect...unused polymorphic instances" should remove any unused instances and automatically remove them from the build and is mostly for saving some space. Is this older code that you have opened in LabVIEW 8 or was it all developed in 8? If it is older you may try to Mass Compile it to make sure that all of the VIs are linked correctly. One last thing to try is addressed by this KB:
This is in LabVIEW 6.1 and should be taken care of in previous releases, but its something to try before you have to go through you code to try to find all of the polymorphic VIs.
Hope this helps!
Andy F.
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National Instruments