I’ve got the same problem, and I’ve always had it. Everything I try to tweak on Firefox either cripples the browser or does not help at all. This “feature” has resulted in me losing edits, images, and other updates. It is the most goddam annoying thing I have ever encountered w/r/t WordPress. (And don’t tell me it’s not a WP problem: I don’t have this issue with *any* other sites, pages, etc.)
If someone has a *usable* fix, please post it. Reward money may be involved. I am damn tired of this, and hate the idea of having to use Internet Exploder to update my weblog.