It may help to know what model # your STB is. Please describe what you mean by freezing (you're watching the channel then...). Have you tried changing the channel, then changing it back? Have you tried an STB Auto Correct? What is the SNR Level reading in your System Diagnostics?
Auto Correct Pathway (Choose One):
Menu > Customer Support > Fix FiOS TV Issues > OK
Menu > Customer Support > In-Home Agent > Fix FiOS TV Issues > OK
Menu > Customer Support > In-Home Agent > Set Top Box Auto Correction > OK
Regardless of which pathway you choose, they all lead you to the same place. After entering the Set Top Box Auto Correction menu, use the navigation arrows to highlight Auto Correct My STB/DVR, then press the OK button, then press the Right Arrow button. On the second page use the navigation arrows to highlight the box(es) that are malfunctioning, pressing the OK button to select each one (OR just press ' 1' to select all the boxes at once), then press the Right Arrow button. On the third page press the Right Arrow button. The box(es) will reset. Check to see if your problem is solved.
System Diagnostics Pathway (Choose One):
Menu > Customer Support > System Information > Info
Menu > Settings > System Information > Info
SNR Level = ?