I have a few of the item in question and it was only cheap so am waiting on a reply from them. 

 

The only thing that makes sense is if they are continually buying items using the cart and when they pay they do not uncheck the box for my item which they may not want anymore.

I was away in Brisbane when lo and behold I hear the familiar tone of a payment being received from my phone. Turned out the last eCheque cleared and although they never responded to the question I sent it must have been enough for them to work out the issue they were having. 

I also had a buyer purchase 4 pairs of shoes in late December and the payment was to come through by e-cheque. This buyer has bought several things from me over the past year and always pays, though every time it's a bit of an ordeal, because it's always an e-cheque, it always cancels the first time and then paypal or ebay or whomever tell me to let the buyer know...and the e-cheque payment attempt doesn't seem to repeat.

Eventually, about 3 weeks later, the payment finally goes through. UGH.

Patience is a virtue! Just think of it as the item being better on the 'sold but awaiting payment' pile than on the 'unsold' pile.