The thing is that if it is often/always the same ad, I can block it, but it if it is due to something else than the ad itself, blocking it will be useless.
There was previously one case of an ad causing problems (but just for Swedish users it seems), but that was systematically the same ad.

I asked about the Firefox version since it seemed a problem that occurred on old versions, like an old version before the v35 (current being v36) it could also be an incompatibility with that.