Same JS error as Bug 355194 is issued on Thunderbird trunk - version 3.0a1 (20070411) on Win-XP SP2 - when "Rebuild Index" is executed. Difference is line number only. > Error: uncaught exception: [Exception... "Component returned failure code: > 0xc1f30001 (NS_ERROR_NOT_INITIALIZED) [nsIMsgFolder.updateFolder]" > nsresult: "0xc1f30001 (NS_ERROR_NOT_INITIALIZED)" > location: "JS frame :: chrome://messenger/content/widgetglue.js :: > RebuildSummaryFile :: line 249" data: no] According to Bug 363008 Comment #1, it seems that "mail loss" didn't occur previously even the JS error was issued. However, when Thunderbird trunk, mail of the folder is lost after the "Rebuild Index" failure . - "Click other folder then click back" has no effect - Restart of Thunderbird has no effect - No mail in the folder is displayed (Mail data is not erased at this step) - If compact folder is done or some mails are put in the folder, all previous data in the mail data file is lost. Further, "delete .msf & restart Thunderbird" won't recover the mail folder and all mail in the mail folder is lost. This means that manual recovery of .msf file (delete .msf and restart Thunderbird) won't work. I think this is Core bug, but initially open as Thunderbird bug. Please change to appropriate one.

this will be fixed by https://bugzilla.mozilla.org/attachment.cgi?id=261276&action=edit the data isn't gone - if you rebuild the index with a build with the above patch applied, your messages will re-appear.

fixed by checkin for patch in bug 196732

there's no dependency here...

(In reply to comment #2) > fixed by checkin for patch in bug 196732 Verified with Tb latest-trunk nightly - version 3.0a1 (20070413). 1. "Rebuild Index" successfully displayed all mails in the mail file. - Remaining issue : Error console message of Bug 355194 is still issued. 2. "Deletion of .msf & Restart Thunderbird" works well again as before. - Remaining issue : Message count is still displayed as "???" until first folder click, if and only if the mail folder file is newly copied one. (This is already reported phenomenon in other bug, and still remain.) Thanks for very quick fix.

Note: Count problem of 2. in comment #4 is a variation of phenomenon by Bug 363008.