My issue turned out to be because the control is being shown in a modal popup (using Ajax Control Toolkit), and I had to make a change to the way jCrop() is called so that it is done on mouseover of the crop image, rather than on document load (so changed CropImage.cs). I found this suggestion on the Deep Liquid Jcrop Google forum – there’s a few related/similar posts about it, the solution I used is Comment #7 at http://code.google.com/p/jcrop/issues/detail?id=16

Unfortunately this means that the crop handles wont show up until the user moves their mouse over the image, but it’s a semi-satisfactory workaround. Any suggestions on how to resolve this so that it works properly with the cropping control inside a modal popup dialog would be great!