Adding myself to this! Applied earlier in March as family of three - myself and two young sons.
Application package got returned as one out of three apps were incomplete - I missed checking ONE BOX as Yes/No! That was it. Eugh.
Anyway, I checked appropriate box, wrote cover letter and reattached the receipt for family payment. Very confusing letter from CIC stating that payment wasn't made etc. But from this forum I've confirmed that original payment receipt is still valid. Thank goodness.
So will start studying for exam and hoping I get my citizenship before PR runs out in November!
Based in Vancouver. Wish me luck!