哪位高手能解决：Cannot modify object ... FIXED property found.的奇怪问题

遇到个奇怪的问题：新的网表与旧的不同，删了些元件。导入新网表后，提示Cannot modify object ... FIXED property found
我先选unfix图标 ，然后右键unfix all，然后导入网表，就报错。也试过把symbol,net,comps,...等全部做一次unfix还是不行。报错信息如下这样子：
Component 'C579' deleted.
         Component 'C560' deleted.
         Component 'C578' deleted.
         Component 'C577' deleted.
         Component 'C559' deleted.
         Component 'C558' deleted.
         Component 'C576' deleted.
         Component 'C557' deleted.
         Component 'C575' deleted.
         Component 'C574' deleted.
         Component 'C556' deleted.
^
ERROR(SPMHNI-95): 'Cannot modify object ... FIXED property found.' -------------------------------------------------------------------------------
===========================================================
End of NETLIST IN Syntax/Logic Check
===========================================================
Total Netlist Warnings =  1.
Total Netlist Errors   =  1.
请教坛子里面高手，我实在搞不定啊

导网表的时候可以选中“Ignore Fixed Property”。