Has anyone else noticed a sharp jump in lag lately?

Normally, my computer(s) have a slight lag issue when lots of things happen on the same screen at the same time (more or less, the game would freeze for a second or two, and then our characters would realign themselves with the server [often after taking a bit of damage], and we'd continue on), but this was infrequent, perhaps once or twice in a 20 minute period.

However, both last night and this morning, all of our computers (including the one that gets lag almost never) have been experiencing a tremendous amount of lag. Roughly once every 8-15 seconds, we've been getting periods where the game will stall for around 3 seconds, then have our characters realign themselves with the server (all commands are still transmitted, as well; if we shield or continue to move, we'll have our shields up when the game catches up). This happens in town and in dungeons alike.

We've tried everything we know how to fix it; less computers on the internet doesn't fix the problem either (I get the same lag when all other internet accessing devices are completely off). It's not my Java, as Minecraft works fine, and all files for SK seem like they are working how they should.

It -possibly- could be our internet, but no other games seem to be having this problem, from what I can tell.

Any help would be more than helpful!