help: DDR2 controller is unstable

I use the DDR2 SDRAM Controller v9.1 and my board is StratixII series. My problem is the ddr2 controller works correctly when the whole project just contains ddr2 controller, but when I add some other modules, the ddr2 controller becomes unstable. The phenomenon is that after I press the global reset(asynchronous), there will be two possible results. One is ddr2 controller works correctly, no data read from ddr2 is wrong, another is ddr2 controller works incorrectly, some data read from ddr2 is wrong. I don't know why. Can anyone tell me what cause this problem? Thank you very much.