According to ESPN, Rafael Palmeiro claimed Miguel Tejada gave him vitamin B12, which caused Raffy's positive steroid test. Tejada claims that he gave Palmeiro the vitamin a long time ago and that probably had very little to do with the positive test, and that he doesn't feel guilty about it because "Vitamin B12 is legal." Here's ESPN's article:
http://sports.espn.go.com/mlb/news/story?id=2169007
http://sports.espn.go.com/mlb/news/story?id=2169007