IMTU Grandfather invented jump drive by detonating a jump interface device that created a transition 'membrane' between our universe and the alternative dimensions of jump space.
This propagated as a bubble at light speed across the galaxy, slowing as it reached the galactic core and the massive black hole there.
This really upset the civilisations on the other side of our galaxy, and since a few of these predate the Ancients (a couple are a lot more advanced, especially the one harnessing the power from the black hole core of our galaxy) a counter device is detonated that is designed to restore stability to their psionically based jump access/teleportation technology.
Unfortunately this counter wave has the effects documented for the empress wave, in it's wake jump travel is more 'interesting' for a few years, and psionics are disrupted or augmented as detailed.
If you find the Dave Nilsen interview from a few years back - someone will have the link to it - he details what the official TNE effects of the Empress Wave were going to be, but he never revealed what actually caused it.
Hence the back story for MTU (I have a much more detailed and longer version, but you get the idea).