In my building we have a few powered speakers that are daisy chained together signal-wise. These speakers are exhibiting a huge amount of hum and noise when they are not receiving a signal. I pulled one down earlier today to do some testing. When I went to put it back into place, I had no signal running and the signal cable to the first speaker in line had actually been removed, the xlr cable's connector arced really badly to the xlr jack/speaker chasis. The speaker was turned off, but did have the power plugged in. Assuming that any damage was already done, I unplugged the power cable and then tried to plug the jack again and got no arc. Any ideas as to what's going on here?

Either you have an AC power wiring problem (Hot to Neutral swap) or one of your components has a big wiring problem.

Ok, the weird thing is that the speakers have been working for several months, they just have a crazy amount of noise on them. Wouldn't any wiring problems that serious mean that they wouldn't function at all?

Hi
There are many ways to wire stuff incorrectly but if your powered speaker gets 'power' on it's mains connection, and some audio, then it will 'work'.
You must get an electrician to look at the whole installation as it may be your 'grounds' are not actually grounds at all. Getting a 'spark' is NOT a good sign so you need to establish exactly what IS grounded and what is not.
Matt S