It is come to our attention that some people seem to remember women offering prayers in General Conference.
While there is missing data from October 2007 that keeps that door cracked slightly, the overwhelming evidence is that members of the Seventy and Presiding Bishopric have offered all the General Conference prayers for the past ten years and likely beyond. For your reference, here is a listing of nearly all of the invocation/benedictions from the past ten years of General Conference.
This data is pulled from the summary of General Conference found in each Ensign (references below). October 2012 did not include a summary, so these were pulled from the session videos.
October 2007 was unavailable in both the Ensign and video.
UPDATE: October 2007 data has been found (thanks, Ziff!).