I noticed this first with the scrollbars in IE10:
Some user interface elements show the same box as well though. Here is a dropdown box from NetLimiter:
Given that that box looks like the "missing character" symbol used in font rendering, I believe this is somehow related to a font issue. Though I haven't been able to figure this out. The only font I know that's used for UI element rendering is Merlott, and that one looks fine.
The scrollbar arrows are now drawn using specific characters pulled from the Segoe UI Symbol font. [1]
These square boxes being drawn indicate that Windows can't find the font or load it properly, or can't display the character correctly for whatever reason. People usually see this happen if the Segoe UI Symbol font became corrupted or is missing.
The solution, here, is to somehow reinstall the Segoe UI Symbol font. You can do this by finding the .ttf file for the font on an existing Windows installation and then installing it on your computer. There were places where you could download it online, but they weren't sanctioned by Microsoft and were taken down, from what I can tell. You can see if you can find it that way too, however.
There may be a copy of the Segoe UI Symbol font in the "C:\Windows\winsxs\Backup" folder.
See "Internet explorer 10 on windows 7 x64 using the wrong image for its UI buttons" for additional information.
You may be able to use the Microsoft Update to Segoe UI Font download to fix this problem. (If that link doesn't work, try searching for "MS Fix KB 2729094.")
