The Event

In the year 1059 something terrible happened.
After Emperor Harriman had consolidated his hold on the Galactic Coalition of Worlds and it's surrounding territories, he set his sights upon Corporate Space. The Corporations strongly resisted this incursion.
Each side had secret weapons;
Through the auspices of Seraph Industries, The Corpo's had limited use of Interdiction Technology that could forcefully pull a ship traveling through fold-space back into real space.
The Harriman Empire had the highly unstable technology that could create a fold-jump, which could traverse great distances in fold-space in the blink of a many-faceted eye.
In 1059 RE these two powerful and dangerous technologies came into violent and catastrophic contact with each other in an otherwise unremarkable portion of the galaxy.  This disaster lead to the end of the Imperial-Corporate War.  Not because hostilities had ended, but because space travel no longer worked the way it used to.
Fold-space was always a non-Euclidian nightmare.  After The Event it began to take on aspects of actual nightmares.  Hints, rumors, and old spacer tales of things that go bump in the dark of fold-space, became documented, if rare, facts.  
Before The Event, a ship could travel about a lightyear's distance in fold-space over the course of a day.  Now the farther you go in fold-space, the longer it takes.  Stay too long in fold-space and things come after you.

Fold-space travel after The Event

Distance in Real Space	Time in Fold-Space	Chance of Unnatural Encounter
1 lightyear	1 day	1% (1 in 100)
2 lightyears	3 days	5% (1 in 20)
3 lightyears	7 days	10% (1 in 10)
4 lightyears	14 days	17% (1 in 6)
5+ lightyears	23 days - eternity	25% - 100%