I think that that's what they're called. Picture here:
Luckily that ship kept that red line for a long time, enough for me to see it and decide to SS it with Fraps. Similar things happen with the orange jet booster thingies on the SCV's backs.
One thing I'd also like to point out is that, if this isn't an innate problem with Fraps itself, the actual graphics I see while playing SC2 are much lighter than the screenshot and may be overall smoother.
The problem is that there's a bunch of graphics problems. Borderlands, for instance, will run things at the lowest settings though all the options are set to the highest possible. And graphic artifacts will appear in Borderlands, too.
Also, I found out that recently that there was a thunderstorm early in the morning, if that would make any impact (which seems possible).
Nothing besides that thunderstorm varies from last night and today; I have not messed with anything inside the case, and I only opened it after seeing this problem to check if all the fans were working. GPU-Z and other programs recognize the graphics card, and other checks seem to say that everything's working fine.
Anski says it's possibly an overheating issue. I would assume that's possible, but it seems just unlikely as there's been very little change from yesterday and today.
Irock says it's dust, but I don't think one month's worth of dust could possibly be enough to affect my computer this much. And the difference only occurred between yesterday and today, so I doubt one night could be sufficient.