I noticed this behavior since a month or two. I didn't have spare time until now to report it. I'm using homemade version of lightning - built with Thunderbird "Daily" - on my Archlinux. Every single time I launch Thunderbird "Daily", I have the account sign in window which appears, asking me to log in to my account. When I run thunderbird from command line, I got a lot of errors looking like this one : Exception: [Exception... "[JavaScript Error: "Could not extract integer from ":0"" {file: "resource://calendar/modules/ical.js" line: 103}]'[JavaScript Error: "Could not extract integer from ":0"" {file: "resource://calendar/modules/ical.js" line: 103}]' when calling method: [calIRecurrenceRule::icalProperty]" nsresult: "0x80570021 (NS_ERROR_XPC_JAVASCRIPT_ERROR_WITH_DETAILS)" location: "JS frame :: file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js :: calStorageCalendar.prototype.getRecurrenceItemFromRow :: line 1899" data: yes] 1: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:2440] calStorageCalendar.prototype.logError 2: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:1764] calStorageCalendar.prototype.getAdditionalDataForItem 3: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:1620] calStorageCalendar.prototype.getEventFromRow 4: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:1565] calStorageCalendar.prototype.assureRecurringItemCaches 5: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:721] calStorageCalendar.prototype.getItems_ 6: [file:///home/fred/.thunderbird/rcqywjg5.default/extensions/%7Be2fda1a4-762b-4020-b5ad-a41df1933103%7D/components/calStorageCalendar.js:664] calStorageCalendar.prototype.getItems/<

Nightly test builds use the experimental icaljs library by default. The console error you see is a known bug in this library and tracked with Bug 1294668. You can work around by switching back to the stable libical library by setting the preference "calendar.icaljs" to "false". How do you connect with Google Calendar? Are you using the built-in CalDAV provider or the Provider for Calendar extension? For CalDAV provider there exists Bug 1301422 that seems to be regressed by changes to the password manager.

(In reply to Stefan Sitter from comment #1) > Nightly test builds use the experimental icaljs library by default. The > console error you see is a known bug in this library and tracked with Bug > 1294668. You can work around by switching back to the stable libical library > by setting the preference "calendar.icaljs" to "false". Ok. Will use it. Thanks for the info! > > How do you connect with Google Calendar? Are you using the built-in CalDAV > provider or the Provider for Calendar extension? For CalDAV provider there > exists Bug 1301422 that seems to be regressed by changes to the password > manager. Provider for Calendar extension built with thunderbird.

Oops ! I was using built-in CalDAV apparently. Disabling it seems to fix this bug. I will reset calendar.icaljs and see if it is a duplicate of bug 1301422

Resetting calendar.icaljs and no prompt asking me for my username / password. Looks like it is a duplicate of bug 1301422 :(