When a user adds an account root Node (from the Accounts panel) as Tab and
changes to it from a different account, it has been reported not to work if the
Accounts panel is collapsed.

Created an attachment (id=8205) [details]
QF 4.5 prerelease 52

This version does "a bit more" by calling the Postbox specific functions
directly when the folder is a "top level" / account folder. It will also show
specific debug messages provided debug mode is active and 

extensions.quickfolders.debug.folders.select = true

debug log:

QuickFolders {FOLDERS.SELECT} 20:4:49.492  [10227 ms]    
QuickFolders_MySelectFolder: imap://xxxx.xxxxx@imap.googlemail.com
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.492  [0 ms]        
try to find open tab with folder...
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.494  [2 ms]        
...folder is currently not open in any Tab.
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.494  [0 ms]        

This is a ROOT folder
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.494  [0 ms]        
Postbox: need to select different account idx: 1
 ----------
QuickFolders {EVENTS} 20:4:49.496  [2 ms]        
FolderTreeSelect: event target = [object XULElement]
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.504  [8 ms]        
Postbox: EnsureFolderIndex : imap://xxxx.xxxxx@imap.googlemail.com
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.504  [0 ms]        
result index = -1
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.504  [0 ms]        
QuickFolders_MyEnsureFolderIndex - index of xxxx.xxxxx@gmail.com: -1
 ----------
QuickFolders {FOLDERS.SELECT} 20:4:49.505  [1 ms]        
Could not find folder in tree (folderIndex = -1)
 ----------
QuickFolders {EVENTS} 20:4:50.283  [778 ms]      
FolderTreeSelect: event target = [object XULElement]
 ----------
QuickFolders {EVENTS} 20:4:50.284  [1 ms]        
FolderTreeSelect selecting folder  Inbox

Created an attachment (id=8206) [details]
QF 4.5 prerelease 54

Bugfix - supersedes previous version and also gives more detail in error
console. It ignores the folder flags and determines whether the folder is an
account by looking at

(msgFolder.rootFolder.URI == msgFolder.URI)


in this case the folder is assumed to be a root folder. Additional
Postbox-specific code makes sure the selection in the account tree is carried
out.

Release 4.5 - Resolved Fixed