Hi,
Could be cosmic rays...not kidding here...was just reading a couple days ago about them affecting PC's and such....
I have my router running on my UPS (battery backup) to make sure power is cleaner...
Could be over-heating... I have my router in vertical position to help create a natural air flow inside the unit....
Could be the unit is beginning to fail.....
Could be somebody messed with it to bust your chops.....hope this is NOT the case....I'd be plenty angry if it were....
SD1