I can't reproduce any issue on Windows 10 64-bit with an nVidia GTX 1070 - it looks like this, which AFAICT is correct: https://dl.dropboxusercontent.com/u/15217362/9patchrendering.png
It never changes as I scroll/zoom around.
Graphics drivers are total garbage and I definitely can believe that two vendor's drivers are broken. Graphics vendors optimise like mad for the latest AAA game releases, and they often break less used apps. It is entirely plausible that both vendors made some optimisation for a recent game that breaks C2.
It could be an issue with C2 itself, but there are two points against that:
1) I should be able to reproduce it in my copy of C2, but I cant, suggesting the C2 code can work at least sometimes, and
2) it ought to reproduce in both the 32-bit and 64-bit versions identically if it's a logic problem with C2's code, since we compile the same source code for both builds.
So this seems like it could be some kind of 64-bit driver issue, but I have to admit, I'm not sure. These kinds of problems are notoriously borderline-impossible to solve. We've had a bunch of them in the past. At least this isn't a serious one - we've had "C2 crashes on startup on all Radeon cards of this model" in the past...