There has been two updates to Lightning today, 1.0b5rc2 & 1.0b5rc3. These releases candidates addressed:
- Alarm window disappearing
- Misplaced beeps from the alarm system.
- Some calendars are no longer working (specifically, webcal:// calendars).
- Support for Thunderbird 5.0 and 6.0
Lightning 1.0b4 will not work with Thunderbird 6.0 Beta, even if forced. However, the current RC builds of Lightning 1.0b5 do support Thunderbird 6.0 Beta and it appears will work the current Provider for Google Calendar 0.8 (which will need to be forced to work with Thunderbird 6.0).