Something is wrong with session restore on trunk, currently it restores an old session (most of the time). Maybe because the session restore backend changed and the SeaMonkey front end needs to be adjusted to that. This is a regression, not sure yet when this regressed.
At least for me the bug seems to be gone. Build identifier: 20130809003001
Yeah, looks like the bug is resolved. I've heard Bug 886116 fixed this. I still want/need to test if aurora has also been fixed.
Looks like everything is fixed. => wfm