Since yesterday, whenever I double click to open a message in inbox it opens a "compose" window similar (but not quite) to the one you would get if you selected "reply".
If I right click on the message in inbox and select "open message in new folder" it behaves normally. Other folders seem OK, this is only a problem with inbox.
I've installed a new version of Thunderbird portable and copied my profile to it, no change so it appears to be a problem embedded in my profile.
I've emptied the inbox and deleted the inbox and inbox.msf files, no change.