It depends on what you mean by "translate" -- obviously, you can convey general meanings, and so on, but specificity is often lost. A pun, for example, can be untranslatable; music -- alliteration, assonance -- is hard to mimic, especially if we're talking about distant languages.
A practical example:
I remember trying to translate Alexander Blok's Ночь, улица, фонарь, аптека... (Night, street, lamp, drugstore) and immediately ran into a couple of problems:
1. The sharp, clashing sounds of the above heightened the imagistic differences. In English, there are no synonyms with similar effects, and you're forced to make a decision: use archaisms, which obscure the conversational tone of the Russian ("Nox, pavement, pharos, drugstore"), sacrifice the music but be specifically English and faithful to the meaning of the Russian, or, of course, a combination of the two.
2. Rhythm -- obviously, this is always an issue.
3. The lack of articles in Russian conveys a slightly sinister element here, while remaining natural, everyday Russian. Obviously, not introducing the articles in English is a problem.

