LeighFox, I've had the same problem with Chummer and Knowledge skills. The part I find really odd is that it happens (normally) under one of the following 2 conditions:
1. You have a lot of specializations; OR
2. When you save the character you are on the Skills tab.
I actually reported this on Dumpshock, and I wasn't taken very seriously, so I'm not sure if anything is going to be done about it. I've also noticed that if you have the same skill with 2 different specializations (say Combat Tactics, one with Hostage Rescue and the other with Urban, for example), after you save the character in career mode it makes both specializations the same, and it does so in alphabetical order. I've tried opening up the XML file and altering it there manually, but for some reason it just does this.
What I've done is filled out the knowledge skills (so I know how many points have been spent), and then I write down (using word or notepad) the skills and their ratings. Then when I move the character to career mode, I copy and paste into the notes so I know what I've got.
I recommend creating an account at Dumpshock and reporting this in the Chummer thread so they know it isn't just one person having this problem.