I have an odd problem where a one-pixel high white line is displayed through certain letters of text. Almost always only a single character type is affected at once, and only in one font size (though that size can change over time). Most of the time things are fine, but this happens several times a day. It's been happening ever since I upgraded to 10.10.

I have noticed few patterns: It might be a problem with Firefox (I'm currently using the nightly ppa, but it occurred in 3.6 also) - but this could just be because I spend most of my time on my computer either at a browser or text editors. I seem to remember it happening with the buttons on various Gnome dialogs. It never occurs in text I've typed, be it an email, url bar, etc. In Firefox it happens across tabs, and the problem remains even if they are closed or reloaded; only restarting the program can fix it.

Two examples (in the first, only the larger "r" is corrupted):

Any help would be appreciated, thanks.