Are you saying that PA taxes were withheld on your checks, however, payroll was SUPPOSED to process Oregon payroll taxes? Is that correct? That is quite a mess. Your employer w/h the wrong state. PA has money it was not supposed to receive. The records your employer filed with PA are now incorrect. I would suggest that you hire a OR CPA to help with the taxes, and helping with the payroll issue, as well as coordinate working with the PA CPA to spring the tax funds from PA. One big REASON employers pay taxes directly to the state is because the state wants to make sure the tax money makes it to the state so they funds are taken right out of your pay. PA isn't going to be anxious to hand over tax revenues, to anyone, without following PA's procedures. The OR CPA probably won't be the best person for the PA issue - but they can help coordinate things with a CPA from PA that has experience in such matters.
You should talk to the employer who ran the payroll and it should be on their dime to fix this error. If they have a good payroll department or use a large agency such as ADP then this should be able to be fixed by the people that made the error. If you have to hire a CPA and or tax attorney to fix this for you I would talk to your employer about them providing reimbursement for all costs if this is their error.
This answer is based on general legal principles only and is not intended to provide specific legal advice. This answer is for informational purposes only and does not constitute the formation of a lawyer-client relationship. Any reader of this answer should not make decisions based upon in without first directly consulting with an attorney