Rated 4 out of 5 stars
I'm using this plugin to avoid multiple master password prompts in my Thunderbird 3.0.1 with Lightning1.0b2pre (the bug that Lightning asks for your master password for each CalDAV calendar in TB3 is known).
Although TB3.0.1 says that StartupMaster 1.2 isn't compatible, it works like a charm in Windows XP. However, in Windows 7 it doesn't. The promt appears before the Thunderbird window opens, but still multiple times :/