If you have a good memory (or just place them side-by-side), you should recognize Psalm 13 here. The similarity goes well beyond the famous line about the fool. There’s some kind of story to this text history, but how that story goes and just how early it is, I do not know. It would be interesting to know if the text corruption–or whatever it is–is pre-Septuagintal, but I doubt we have access to that information.
Since it’s been two years (!) since I translated Psalm 13 for this project, I’ve gone ahead and just re-translated from scratch without looking at my earlier work. You could amuse yourself by comparing my translation of the duplicated material to see what changes I’ve made.
“Dixit insipiens” (Psalm 52)
 In finem, pro Maeleth intelligentiae David. Dixit insipiens in corde suo : Non est Deus.
Unto the end, for Maeleth. Thoughts of David. The fool has said in his heart, “There is no God.”
 Corrupti sunt, et abominabiles facti sunt in iniquitatibus; non est qui faciat bonum.
Corrupt are they, and made abominable in injustices; there is none who would do good.
 Deus de caelo prospexit super filios hominum, ut videat si est intelligens, aut requirens Deum.
God down from heaven has looked forth above the sons of men, that He may see if there is one understanding or seeking God.
 Omnes declinaverunt, simul inutiles facti sunt; non est qui faciat bonum, non est usque ad unum.
All have fallen low, alike have been made useless; there is none who would do good, not even to a single man.
Nonne scient omnes qui operantur iniquitatem, qui devorant plebem meam ut cibum panis?
Shall they not know, all who work injustice, who devour my people like a food of bread?
 Deum non invocaverunt; illic trepidaverunt timore, ubi non erat timor. Quoniam Deus dissipavit ossa eorum qui hominibus placent : confusi sunt, quoniam Deus sprevit eos.
God they have not called on; there have they trembled in fear where there was no fear. For God has strewn the bones of them who are pleasing to men; they are scattered, for God has scorned them.
 Quis dabit ex Sion salutare Israel? Cum converterit Deus captivitatem plebis suae, exsultabit Jacob, et laetabitur Israel.
Who will give from Sion the salvation of Israel? When He shall turn, shall God, to the captivity of His people, Jacob will exsult and Israel be gladdened.
v. 1 pro, Maeleth, intelligentiae, David. Good luck deciding how to carve up those words. Not knowing “Maeleth,” you could write “for the Maeleth of understanding”–whatever the heck that means. Not declining David, you could take it as any number of cases–to or for David, apposite to Maeleth, genitive, etc.
v. 2 qui faciat This is a nice little piece that’s easy to lose in the English–that’s a subjunctive verb, so we’re actually talking about some sort of characteristic, not a simply factual claim that “no one is doing good things right now.” “There is no one who is the sort of person to do good” is the idea. Seen again in v. 4. [Post-script: boy do I feel silly for not pointing this out in my Psalm 13 comments!]
v. 4 declinaverunt Lots of options for how to take this multi-purpose word. “Declined” is cheating but very tempting here. You are somehow moving off the “true line,” whatever that is and in whatever orientation you prefer to take it. The prefix strictly calls for a downward motion though, hence “fallen low.” I’m ambivalent about using “fallen” but we all have our limitations.