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Tabs disappeared in Firefox 20 Rated 4 out of 5 stars
I was having the exact same problem as others, where my groups disappeared in Firefox 20. I was only saved by using Session Manager.
Update: Fixed by installing https://docs.google.com/file/d/0B_cPIh38WTUSc0hiM3VCUVRlVk0/edit?usp=sharing.Though my pages are out of order now.