»prove{n,d}

During a conversation I found myself vacillating between proven and proved. A cursory look through the dictionary proved them equivalent:

(v) prove, turn out, turn up (be shown or be found to be) (v) prove, demonstrate, establish, show, shew (establish the validity of something, as by an example, explanation or experiment) (v) testify, bear witness, prove, evidence, show (provide evidence for) (v) prove (prove formally; demonstrate by a mathematical, formal proof) (v) test, prove, try, try out, examine, essay (put to the test, as for its quality, or give experimental use to)

Ditto proven; so why did the particples cause me such confusion? I think I expect the weak version (proven) to accompany a verb of being (e.g., I was proven wrong), and the regular particple form (proved) to be the simple past tense, or the second verb in a compound with a helper such as had: I had proved the theorem.