You get them wrong 'cause you don't know what they are. They are to test your reasoning power rather than verbal skills. They are known as Critical Reasoning (or CR in GMAT jargon)
They are quite easy and if they come in verbal section people who skip them will be at competitive disadvantage, 'cause most of you will be leaving 5 inappropriate usage questions, plus the general accuracy in verbal is low. RCs were easy last year but in 2001 and 2002 they were very ambiguous.
Given this, it is not at a wise decision to leave CRs provided they make a comeback
How to prepare?
1/ GMAT guides
2/ online: just google "Critical Reasoning"
Enjoy!!