AP

My I-140 has been approved, and I-485 is ready to go to INS. I am also applying for AP and EAD. Previously, my understanding regarding AP was that, with AP, we could definitely re-enter USA after traveling outside USA (i.e., visiting parents, relatives, and friends in China). However, I was recently told that there is still a possibility for a person with AP to be refused to re-enter. Is this true?