This is a bug with Kate. But if you disable the session auto save, it loads the plugins. You can do this by changing the Application Startup Behavior to Start new session. Application Startup Behaviors can be changed from Settings > Configure Kate > Sessions. This is not a fix, just a walk-around.
I actually had this same problem not long ago. I have since fixed the problem. Unfortunately, what i did wasn't pretty. I created a new account and then deleted EVERYTHING from my home directory and moved everything from the new account to it. Meaning that I had to reconfigure everything. Of course, shortly after that I found a possible solution to the problem. The problem MAY be caused by a corrupted highlighting definition file. To easily test this try disabling highlighting and see if the issue goes away.
If that worked for you then you'll need to get another copy of your highlighting definitions which aren't borked. You say you can use other accounts just fine so try to just use the ~/.kde/share/apps/katepart folder from a working account in your account. Just delete yours and copy the other over to the same place in you profile.
Best Answer
It seems one cannot highlight leading spaces.