Brazil was one of five countries to abstain in the vote to approve use of force in Libya, and particularly given their UN Ambassador's comments, it strikes me as a particularly cowardly vote.
Among the five governments that abstained in the vote, Brazil’s U.N. ambassador, Maria Luiza Riberio Viotti, voiced concern that military action in Libya would “exacerbate tensions on the ground and cause more harm than good to the same civilians we are committed to protect.”
She also warned that military action would undermine the “spontaneous homegrown nature’’ of popular uprisings spreading through the Arab world and threatened to “change that narrative in ways that would have serious repercussions” for Libya and the rest of the region.
If you believe that firmly that military action will have very negative consequences, then vote no. Instead, Brazil is trying to hedge its bets. Abstaining means it is trying to avoid blame for the consequences of military action, but also does not want to be blamed for "doing nothing."