"What is with the lamp?"

Translation: Was ist mit der Lampe?

[verotero]

der Lampe or die Lampe¿

[Katherle]

After the preposition "mit", you have to use the dative case. That's why "die Lampe" (feminine nominative) becomes "mit der Lampe" (feminine dative). So the sentence Duolingo gave you is fine, whereas *"Was ist mit die Lampe?" is wrong.

See also:
http://german.about.com/library/blcase_sum.htm

[verotero]

ok, thanks!

[Mantonization]

Just to clarify, this phrase means the same in German as it does in English, right? "What is (up) with / wrong with the lamp"?

[AdriaanRetief]

It does indeed. You could also ask a person, "What is with you?" which would mean the same as: "What is wrong with you?".