Image resizer not working with Nivo slider

I've been trying to use Image Resizer in conjunction with with the Nivo Slider image rotator.

I appreciate that its probably more to do with the Nivo Slider, than the Image resizer, but I thought I'd run it by you guys in case you've come across anything similar before.

I've got a test page with two images. When the page first loads, the image is constrained horizontally, but not vertically. Once it goes to the second image, and every time after that, the image seems to get chopped off at the bottom, and just before it changes sort of jump to the correct size and proportion.

You can see what I mean here:

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The two smaller images on the left hand side are resizing correctly, which is why I figure the issue is with the rotator, so feel free to pass the buck after the quickest look.

Thanks.