Hello,
I've used CCleaner as long as I can remember, and I've never had this problem with Firefox until the newest build. I have a nice bunch of saved passwords on there, and I noticed that CCleaner deleted it!!!! Now, I've sense put them back in, that's not the problem, but I just wanted to bring this to your attention. I've included the 3 files below that were shown after the deletion that includes Firefox. I'm assuming it's the "signons3.txt" file.
C:\Users\Owner\AppData\Roaming\Mozilla\Firefox\Profiles\vgeb9xad.default\downloads.sqlite
C:\Users\Owner\AppData\Roaming\Mozilla\Firefox\Profiles\vgeb9xad.default\signons3.txt
C:\Users\Owner\AppData\Roaming\Mozilla\Firefox\Profiles\vgeb9xad.default\formhistory.sqlite