so tired of this... roamio pixilation and lock up

My Roamio Pro started locking up 1 year ago. Sent the unit back and got a new unit. 4 months later, same thing. TivoMargaret told of a new update to stop lock ups. Several weeks later, it fixed the lock up. In June 2014, it started to lock up again. Called weakness for warranty repair. Sent the unit in (at a $55 shipping cost), was told there was nothing they could find that was wrong with the unit but was replacing the unit anyway just in case. Now, 3 months later, tonight, while recording 4 hd channels, total lock up with extreme pixilation. A hard reboot was required. 40 minutes later, SAME THING! The unit is plugged directly into the power outlet, no ups. I have 1 other roamio pro and it works fine, a 1 tivohd and it works fine. What do I do now ? Please help.