I have had a 540 for years now. In searching the S03 Error threads I see that I too had this issue with Direct TV a long time ago and had forgotten. I switched to Dish and the problem went away.
But now I switched it back to Direct TV and low & behold it's back. So the problem has been there all along.
I am using a powered OTA antenna and an old Hughes Direct TV box. The box I had last time was an RCA. I "think" the problem went away when I used cable for locals for a short time but I'm not positive.
I have repeatedly tried code 57 & 58 & I think the other was 52? (don't recall off hand). I'm trying a few more things before sending an email as suggested in one of those earlier threads.
Sadly, my S2DT is suffering from the daily freeze & restart issue.
What burns me up is that these issues have been ongoing for a while now, and that because I have DBS I have to use the 540 & S2DT even though I have a HDTV set sitting in the living room. I would have gotten a Series 3 except I don't want cable!
So here I am stuck in the middle of a 3 year commitment thanks to the contract I entered for 3 years of programming, so I'm stuck even though the equipment doesn't work right.
I am really frustrated here! These have been ongoing problems for quite a while and I am stuck in commitment.