HD Channels temporarily off Air in AZ

This is getting ridiculous. HD FOX and NBC..along with about 10 other HD channels stopped working about 3 months ago. Yes...we have followed all the directions regarding unplugging, etc...had both boxes replaced today....problem is still here!!! Yes i will call a technician...but from previous experience it doesnt help. What is up with Cox network? This is the last time i deal with this as i am ready to switch ...been with COX for 16 years...loyalty means nothing whe the product works like **.