I'm not sure if this is something that I can fix, or if I should file a bug on Bugzilla:
I successfully use Firefox Sync on several instances of Firefox, syncing bookmarks, passwords, history and tabs. The four Firefox instances I'm using successfully are all version 3.6:
- From official Ubuntu repositories on Ubuntu 10.04 (Lucid Lynx)
- From official Ubuntu repositories on Ubuntu 10.10 (Maverick Meerkat)
- Directly from Mozilla on Windows XP
- Portable Edition on Windows XP
When I try to sync it to Firefox 4.0 Beta 6 (the version from portableapps.com) on Windows XP, it will successfully sync bookmarks and tabs. However, it fails to sync passwords or history. No errors show (not even in Firefox's Error Console), and the sync completes quickly.
I've tried all of the following:
- Overwriting the local data with my data in the cloud
- Starting from a fresh download from the Portable Apps site (new profile too)
- Installing the Firefox Sync extension (version 1.5)
- Of course, checking my settings in the Options window
- Toggling "Sync Passwords" and "Sync History" on and off in the Options window (including combinations of restarting Firefox mixed in)
Here's a screenshot of my current sync settings:

I know I'm dealing with a beta here, but I'm not yet sure that I should file a bug about it, either. I haven't been able to test it on an install (I'm using the portable edition because I don't want to risk my current installs of 3.6). Also, I suspect it might have something to do with the format of my data stored in the cloud (I've used the same account since the almost-early-adopter era of Weave).