A Cross Platform Listbox Oddity

I have a dilemma. I’ve been banging my head up against the wall today trying to figure out why my listbox is so fugly in Windows. I’m hoping that one of you cross-platform geniuses can help out.
I’m loading a listbox and adding a picture object into the celltag for all the columns past zero. On the Mac OS X side of things the listbox works great. Here’s the screenshot for it:

Mac With Mask

The graphic has a mask applied to it and in general works great.

So here’s the exact same thing in Windows:

Windows With Mask

Yikes, that’s fugly. A severe case of the jaggies.

Here’s the same thing on Windows with the mask removed:

Windows no Mask

So now we’re close. Just for grins, lets take a look at the Mac version with no mask:

Mac No Mask

As you can see, the Windows version looks a lot like the Mac version.

So my question is, what the heck is happening with the Windows mask? The graphics are being scaled down to the same size on both platforms.

The original graphics are 64 x 64. I’ve also tried them at 16 x 16 and I get the same results. I’ve tried converting the Mac generated graphics so that they use the Windows color palette.

So what are your suggestions?