"R. C. White" wrote
I suspect it happens when one has Quicken "open" a file in the BACKUP folder. When Quicken wants to do its automatic backup, it will just create a new folder, BACKUP\BACKUP. Also could explain the existence of the QDATA21 file referred to earlier; probably let Quicken open the backup file, QDATA2.
I suggest never opening a backup file; either restore it or make a Windows copy of the fileset and open the copy.
A couple of possibilities for the date gap: not running Quicken for some time (probably won't explain the large gap, but can cause gaps like the one "missing Monday"); and using a different Quicken data fileset in a different folder for some period. A Windows Explorer search for *.qdf should find any other BACKUP folders that might be present.
A third possibility is excessive tidiness. :) Concern over mounting numbers of files have caused some folks to start house cleaning without realizing they were deleting valuable files.