We still accept outside releases as long as all the necessary information is covered. 3 things that are required in addition to the legal language are the (legibly) printed name and signature of the model, the photographer and a witness.
The photographer name must match the name on your account (not an agency name for example). If the model is a minor then the printed name of the model is required in addition to the printed name and signature of the a parent or guardian.
The date of the witness signature must match the date of the model signature (they need to actually witness the signing).
Those are the most common issues I've seen with releases. If you still can't figure out what the problem is, send me an email and I'll be happy to take a look.
-Mat