I'm not sure how I can help, are you sure you had threads that were subscribed to before? I took a look at your account in the control panel and I didn't see anything wrong. I did note that you have your account set up to not subscribe to threads that you reply to, but that's about all I could see.
It is possible I guess that if you were subscribed to a thread and that thread was removed or moved that perhaps it would remove it from your list, but that's just a guess. As I said, I don't see anything in your account that would indicate a problem so I'm not sure what info I can offer will help.
Do you know of any threads specifically that you were subscribed to and now are not? If so, please link me and I'll be glad to look further into it.