Hi cbarus,
Relax. Give more info so that Gurus can answer your question.
1. Did your current company gave you an offer letter saying that this is a contract job and not full time job?
2. It doesn't matter how many companies you change after 180 days after filing of I-485. It does matter whether the current job meets the requirement stated in your LC and I-140.
3. If you are thinking that your job letter should contain "PERMANENT" word then you are wrong. They just have to state that so and so person is currently working with us as a fulltime "Title"....etc.
4. You will be in trouble, if the IIO asks you to show all your paystubs and W-2 and you fall way short of what has been stated in your LC.
5. If there is a gap of more than 180 days[i.e., on bench and you do not have paystubs] after filing of I-485.
Gurus please give your valuable inputs.
Otherwise you should be fine cbarus. Do not worry too much. You are in a better position to judge. I do not have more information. If you could post more info, then Gurus might help you out.