Separation and claiming dependents

My now ex-husband deserted the family, but claimed one of the kids as his dependent on his taxes during our separation, so my electronic tax filing was rejected.  My ex husband did not financially support the kids and only lived with the kids for 4 months that year.  Supposedly, he corrected this by amending, but I still could not file for my refund electronically.  How can I file for my federal and state refund?  What documents do I need to submit to the IRS to support that I have the right to claim the kids as my dependents?  And how long will it take the IRS to issue my refund?  Thank you!