Edward IV paternity

I've been following this discussion with a lot of interest and a some thoughts have occurred to me.

Supposedly, Duchess Cecily said Edward was illegitimate during a row over his having married Elizabeth Woodville. I don't know when Edward and Elizabeth married (I thought it was 1464/65?),
but it seems that it took several years (until 1469) before any rumor got about.
At any rate I wrote out the following time line and it brought several questions to mind:

1464/65 - Edward marries Elizabeth Woodville; his mother is furious and supposedly says Edward is illegitimate.
1469 - George, Duke of Clarence becomes involved with the Earl of Warwick and wishes to marry Isabel (Warwick's daughter).
1469/70 - Warwick allies himself with Margaret of Anjou and betroths his second daughter (Anne) to Edward of Lancaster. The Duke of Clarence sides with Warwick. Edward IV is driven from the throne.
1471 - Edward (and Richard) return from exile. Richard (and Duchess Cecily?) convince George to switch allegiance back to Edward. Warwick is defeated and killed. At Tewksbury Edward of Lancaster is killed.
1478 - George, Duke of Clarence is executed privately in the Tower (accused of speaking prejudicially against the King). Robert Stillington is imprisoned.

1) Why did it take four or five years for the rumor to start spreading? Was it because there was a need for it (the rumor) by the Duke of Clarence to bolster his worth with Warwick?

2) Or possibly was it spread by Warwick to make George more valuable and a greater threat against Margaret of Anjou?

At the present I only have a couple of history books for reference, but while looking in "Daughter of Time" to see if there was any more exact dating, I came across the following about the Duke of Clarence:

"The seed was perhaps sown when, during his first backsliding in the company of his father-in-law, Warwick had created him heir to the poor crazy puppet-King, Henry VI, whom Warwick had dumped back on the throne to spite his cousin Edward."

And on the next page:

"At last his folie de grandeur graduated from secret negotiation undertaken on his own behalf with foreign courts to open display of the Lancastrian act of Parliament which had declared him heir to the throne after Henry VI."

Does anyone know how accurate these two extracts are? Is it possible that this was what got George executed and not knowledge of Edward's marriage to Eleanor Butler? And that Bishop Stillington (who had been Edward's Chancellor at one point and was later released) had been scooped up to find out what, if anything, he had told Clarence?

Hopefully the library will soon start coming through with some of the books I have requested. Anyway, I thought the above might be interesting.

PS: I still lean towards the "bastard" theory being a garbled (or self-serving) version of the actual words simply because the Duchess hasn't been shown supporting anyone other than Edward when there were other candidates available. If Edward V wasn't fit to rule because he wasn't legitimate, then why was Edward IV?

PPS: Ask and ye shall receive! "Life and Times of Richard III" just in!

Doug