What's With the New Version of Firefox!?

[macx]

Every time I try to open my Excite email, it quits and the session has
to be restarted or restored.

Also, the same thing happens when trying to open many PDF documents

It's really getting annoying!!

I'm ready to go back to the previous version which was largely
trouble free and did everything I wanted it to.

Anything to do to make the new version work as well as the previous one?

Thanks!!

PS - XP