The confusion may be because the law changed in Sweden in 2001.
http://en.wikipedia.org/wiki/Swedish_nationality_law"Swedish law was significantly amended with effect from 1 July 2001 and from that date, dual citizenship is permitted without restriction."
http://www.swedenabroad.com/Page____33207.aspx"Dual Citizenship
One of the basic principles of Swedish civil law has been the avoidance of dual citizenship. With the adoption of the Citizenship Act of 2001, however, Sweden abandoned this principle.
On July 1, 2001, a new Citizenship Act came into effect in Sweden. The new law makes it possible to have dual citizenship. The law also gives children further opportunity to become Swedish citizens independent of their parents.
If you are a Swedish citizen and become a citizen of a second country, the new law means that you can keep your Swedish citizenship if the other country permits it. By the same token, if you become a Swedish citizen you can keep your foreign citizenship if the laws of that country permit it."