Search the web for "IE10 Flash pixelated". You are not alone. Looks like a general problem with the way Flash is implemented on IE10 -- it is an embedded Flash separate from the other plugins you might have for other browsers.
I figured it out. The Flash version used in Lightroom 4 cannot handle an increase in Windows DPI. In other words, I set my browser to 125%, and this caused the image to pixilate. I also set Chrome to 125%, but chrome detects it is a Flash image and does not increase the DPI for that page.
Is there a way you can a Flash output that can resize, or is that possible?