I'm pretty sure you're talking about lighting glitches where it's all dark with glowstone or 1 block is lit but not others...
If so it'd be:
Stairs/slabs that have light on the other side, making the block that is shown (that is, while and no smooth lighting) all bright, but because it's a slab some of the light is visible.
Your Minecraft Client hasn't found glowstone/torches (needs a block update to register it) and everywhere is dark because of it. Just place a block/break a block right next to the light source.
But either way, if it's that, it isn't the servers fault, that'd be Minecraft.