This affects me as well, I'm using 3.6.4 and I'm syncing everything. The syncs are all up-to-date. I'm using Windows 7 Ultimate on both machines.

Ever since "Tabs from other computers" was turned into a page I've had problems. At first its page just took an unusually long time to list tabs, but now it just never shows any tabs. Lately I've also been getting status bar warnings ("Unknown error") almost every single time the extension syncs.

Both machines are running Firefox nightlies (one OS X and the other Ubuntu) and running the official released versions of Sync.

I'm having this problem too but in addition I'm using Firefox Home app on my iPhone and under tabs I'm seeing two seperate entries, one for each of my PC's, each containing the tabs I had open on the respective PC.

So, it would appear both are syncing tabs correctly with the server, but not between them. Instead they're creating two seperate tab instances...

Firefox Sync / Weave support is here: http://groups.google.com/group/mozilla-labs-weave/topics

Firefox Home iPhone App support is here: https://support.mozilla.com/en-US/forum/6

Click on History, select Tabs from other computers, and you'll see the tabs of your other browsers.

For me problem was the fact that I've "bootstrapped" firefox from another machine by copying whole ~/.mozilla path with all the settings and plugins, hence sync considered both machines to be the same one, so "tabs from _other_ computers" was always empty, even though the rest of the settings synced just fine.

Changing "Computer Name" in sync settings didn't seem to help, but "Deactivating" the device, then setting up sync from scratch worked.

Dunno if the problem is specific to firefox 4 though, as I recall tabs-menu working in ff3, even though I've always cloned ~/.mozilla this way.

I am using Firefox 5.0 You could click on the "triangle" at the top right hand side of the window. And you might find the option to "show tabs from other computer"