White Grapes need help

[uptospeed]

Can anyone help we planted white grapes and red ones over an arch and while the red ones are fine the white ones when they produce fruit seem to shrivel up and go black before they are fully matured.http://www.growfruitandveg.co.uk/gra...s/confused.gif

[Rydeboyz]

Could it be this?:

Royal Horticultural Society - Gardening Advice: Grape Shanking