I have heard from one friend whose friend had the same situation. His wife worked as nurse in China so she came here and work as a nurse directly. Because she didn't go to nurse school here in U.S., she need to pass some English test which she failed many times. Her I-140 has been approved very earlier but her 485 got denied because she wasn't able to pass the English exam in time. To make things worse, her hu*****and has used EAD to work. So when the denial notice was received, it is accomplished with a order of leaving U.S. in certain time limit. Finally they did leave U.S. and went back to China. In China, the hu*****and applied for the H-1 visa and both of them came back. Then she past the exam and she had her case re-openned. Now their I-485 were approved and everyone is happy. I heard that they did try some way to re-open 485, maybe get some help from congressman. Anyway, I don't have direct source for that. Don't worry. I think a lot of people are in the same boat and it is very possible to get your 485 appoved without re-file your I-140. You might not need to leave U.S. if you handle this situation properly. I don't know the details how this couple deal with that. But if you like, you can e-mail me at qmruanc@yahoo.com and I will try to ask the friend who know this couple for their contact information. You might be able to get valuable advice from them.
Don't worry too much. But you do need to act quickly. Good luck