Incorrect Price Showing On Category Page

It's just been noticed that prices are wrong on the catergory page, for example see the following link and look for 'Rhododendron Gomer Waterer' the price is showing as £21.99 but when you click on the product it is only £14.99, seems to be a problem only when an item is out of stock, if i add one back in stock the price on the category changes. There is only one option for this plant so I have no idea where £21.99 is coming from, any ideas?

I see 14.99 everywhere. Fixed?

Not fixed yet but its stumped me.

Yes NOT fixed, but we have added that item back into stock now but if i take it out it still goes back to £21.99