In girum imus nocte et consumimur igni.

This sentence is a riddle in the form of a palindrome -- literally a puzzle inside a puzzle. This particular sentence is called "the devil's verse", see http://www.archimedes-lab.org/atelier.html?http://www.archimedes-lab.org/latin.html for more Latin puzzles.
For the Latin quote of the week, see http://www.dogtulosba.com/archives/cat_quidquid_latine_dictum_sit_altum_viditur.html
For Latin sayings, see http://www.rktekt.com/ck/LatSayings.html
For handy Latin phrases, see http://www.bbc.co.uk/h2g2/guide/A218882
For more palindromes, see http://villemin.gerard.free.fr/Langue/Palindro.htm

You can search for translations on Google http://www.google.com although most of the hits will be for an orchestral composition with that name. Almost every translation is different.

The sentence is difficult to translate because the anonymous Roman author had to use words in uncommon senses in order to make a palindrome. Yet, given that the palindrome is a riddle, it is easy to pick out bad translations.

The answer is a kind of animal. The animal in question has feet but walking is not its best known mode of transportation. Thus, any translation containing the word "walk" is immediately wrong.

People who haven't studied Latin should still be able to pick out the words "night", "consume" and "fire", which could make them think that the sentence has some sort of dark, evil meaning.

Interestingly enough, nox and ignis are both third declension istem nouns. nocte is ablative, and igni is dative, which I think are both the correct cases for their usages. Ablative case marks a location. Dative case marks an indirect object (or the agent of a passive construction).

in means "in", and et means "and".

imus means "we go". It is the firstperson plural present indicative form of the verb ire "to go".

girum is hard to translate. It can be taken as the accusative singular form of the noun girus, but the catch is that girus was not a commonly used word in classic Latin. gyrus is a second declension masculine noun meaning circle, cycle, ring, orbit, or course. The derived giro in Italian means tour, turn, or circle. In current Italian, "andare in giro" means "to go around without a precise intention or direction". Spanish splits the meanings into gira for tour and giro for turn. ("Sunflower" in Spanish is girasol.) Since in followed by the accusative means "into", the desired meaning of girum is probably "circle".

Putting it together so far, in girum imus nocte means "we go into the circle by night".

consumimur is a firstperson plural present passive form, so consumimur igni means "we are consumed by fire".