Here's my two cents.
First, you should be
eating carbs during the day, especially breakfast. I can agree with the no carbs at night.
However, I'm reading your post and you say "about a cup" of rice at night. Depending on your activity level during the day, a cup of rice, in my opinion, will not hinder your ability to lose five pounds.
Losing five pounds will have more to do with cardio and lifting. Of course, you need to eat healthy, but the bottom line is, the more you work out to lose the weight, the greater the chance of your losing it.
If you can, eat a little less and exercise more.
I saw you asked a question "does that mean I can never eat it again?" I'd like to say to everyone out there, there is no such thing!! You can eat anything you want to and still lose weight. How much you lose will depend on your diet and exercise program.
My suggestion would be have the rice for lunch if you can. But if you'd rather have it for dinner, go ahead. I would just increase my activity (exercise) level to compensate for it.