How come every time I open the 4.0 Firefox browser it always does a add on capatibilty check? How do I stop this?

Since upgrading to 4.0 every time I open my browser it keeps doing an add on compatibility check. How do I stop this? Every time it does a check it gets rid of my bookmarks and I have to reload them again, and it also takes me to the Firefox welcome page. How do I stop this as it's a pain in the neck. I hate 4.0 I'm going back to my last Firefox browser as I had very little trouble with it.