Download Page Corrupt Zip File

When rolling your own theme using the themeroller, and downloading, the zip file created is corrupted.

I opened this file in a hex editor, and there was 15 bytes prepended to the usual 'PK' header.

Reproduction steps:

http://jqueryui.com/download/?themeParams=%3FffDefault%3DLucida+Grande%252C+Lucida+Sans%252C+Arial%252C+sans-serif%26fwDefault%3Dbold%26fsDefault%3D1.1em%26cornerRadius%3D5px%26bgColorHeader%3D5c9ccc%26bgTextureHeader%3D02_glass.png%26bgImgOpacityHeader%3D55%26borderColorHeader%3D4297d7%26fcHeader%3Dffffff%26iconColorHeader%3Dd8e7f3%26bgColorContent%3Dfcfdfd%26bgTextureContent%3D06_inset_hard.png%26bgImgOpacityContent%3D100%26borderColorContent%3Da6c9e2%26fcContent%3D222222%26iconColorContent%3D469bdd%26bgColorDefault%3Ddfeffc%26bgTextureDefault%3D02_glass.png%26bgImgOpacityDefault%3D85%26borderColorDefault%3Dc5dbec%26fcDefault%3D2e6e9e%26iconColorDefault%3D6da8d5%26bgColorHover%3Dd0e5f5%26bgTextureHover%3D02_glass.png%26bgImgOpacityHover%3D75%26borderColorHover%3D79b7e7%26fcHover%3D1d5987%26iconColorHover%3D217bc0%26bgColorActive%3Df5f8f9%26bgTextureActive%3D06_inset_hard.png%26bgImgOpacityActive%3D100%26borderColorActive%3D79b7e7%26fcActive%3D2e6e9e%26iconColorActive%3Df9bd01%26bgColorHighlight%3Dfbec88%26bgTextureHighlight%3D01_flat.png%26bgImgOpacityHighlight%3D55%26borderColorHighlight%3Dfad42e%26fcHighlight%3D363636%26iconColorHighlight%3D2e83ff%26bgColorError%3Dfef1ec%26bgTextureError%3D02_glass.png%26bgImgOpacityError%3D95%26borderColorError%3Dcd0a0a%26fcError%3Dcd0a0a%26iconColorError%3Dcd0a0a%26bgColorOverlay%3Daaaaaa%26bgTextureOverlay%3D01_flat.png%26bgImgOpacityOverlay%3D0%26opacityOverlay%3D30%26bgColorShadow%3Daaaaaa%26bgTextureShadow%3D01_flat.png%26bgImgOpacityShadow%3D0%26opacityShadow%3D30%26thicknessShadow%3D8px%26offsetTopShadow%3D-8px%26offsetLeftShadow%3D-8px%26cornerRadiusShadow%3D8px