Error: Unable to update property"I/O standard" for node ddr2_top_dm[0]

Device: Stratix II Gx 30DF780C3

Operate: set the "I/O standard" of pin ddr2_top_dm[0] and other DDR2 controller signals.

Error:Unable to update property"I/O standard" for node ddr2_top_dm[0] and other DDR2 controller signals.

Help: what's matter?