I am using F1.5i SP2, and my Virtex design is getting TRCE and BitGen errors when the CLKFB is not connected correctly. The following TRCE Windows error will sometimes crash the program:
"Abnormal program termination at trce.exe: exception access violation (0x0000005), address 0x01c9162a."
Also, during BitGen, the following error occasionally appears:
"BitGen error: xvkdr: 5 - blockcheck: dangling DLL input pin CLKFV of DLL comp....not connected."
Make sure that the DLL feedback loop is connected correctly; if it is, the error should go away.
This will be fixed in a future software release.