[edit] I looked at your post again, and realize you're just talking about one character who's affected this way; my suggestion is a bit different. Perhaps a vulnerability disad, "takes extra damage from side-effects" would make this more useful to you. [/edit]
I wrote up quite a few effects like this, for a campaign which (sadly) isn't finished yet. I designed it as a "side-effect" limitation on the ship's movement power. There were several types of drives, with different, sometimes unpredictable side effects;
--minor side effects which always occurred. Some were continuous, lasting throughout the trip until the drive was turned off. Others occurred each time the drive was turned off, at the end of the trip. I used this for effects similar to hyperspace travel in the Chanur novels.
--major or extreme side effects which occurred when the drive wasn't used properly. For instance, drives which only work in the "black zone", far from a system's primary, could be activated closer in, but the ship and crew would both suffer the consequences. This would be similar to the "misjump" effect in Traveller, which occurred if the drive was activated too close to a massive object.
This is a very flexible concept; the side-effects and circumstances in which they occur can be defined any way you like. (And you save lots of points on the movement power!) Let me know if you'd like to see some better examples. At the moment it's late, and I've put away all my notes on this.
L8r,
DGv3.0