Diff view: first character weird

The diff view is rendering the first character of each line weirdly. Actually, it looks like it's overlaying a box character on each of them. (see screenshot)

This appears to be only happening in my .NET project, not my Java projects. So perhaps it's an issue related to line endings, or document encoding?

I did not have this problem under v1.7.x (don't remember exactly which version I was on). The bug appeared immediately after upgrading to v1.8.1.0.

Running on Windows 7 Pro SP1 x64