Sounds strange but my remote stops working after 10pm. I can still adjust volume and turn off the tv but all other buttons don't respond. Works fine again in the morning. Did I inadvertantly lock it somehow??
Last year on my first night with FIOS, the same thing happened to me. Perhaps you need to recode the remote. and reset the box. I called support and after that it worked again. Could also be a parental control or something.