I freeze too. It's sort of an automatic protective response. I feel bad about it, but if I allow myself to fully feel everything, I'm afraid I'll completely fall apart, and I can't do that because I'm supposed to be the strong one.
Two examples of when I let the wall fall down:
A cousin of my husbands died in a really grousome car accident a couple of years ago when he was only 18. I tried to explain to dh that I would lose it if he forced me to visit the boy's parents right afterward. He forced the issue anyway. It was really embarrassing, because I did lose it. I don't have very good emotional boundaries and I felt every bit of the parents' pain when I was with them. That's why I protect myself, and when I can't, feel like I'm going crazy.
And when I found out that my little nephew has Hunter disease, which is terminal, I felt my brother's pain like is was my own. I still do sometimes. I have to disengage for things like that somewhat, or I can't function. I can't feel everyone's pain for them, or I won't be able to live my own life. So I do what you do and take refuge in my intellect, doing medical research from afar, or something of that nature.
Ever see one of those scenes on Star Trek where Diana Troy acts as if something tragic were happening, and you find out later she was feeling the emotions of someone else? Well, that's me. I do that. And I don't know how to stop it from happening unless I can get some distance between us.