The dialog appears everytime a file is imported into the playlist, and its tags, MMD file or auto-cue values are loaded. When auto-cue is disabled, and you only import a single file, the dialog might disappear again in the same moment, because the operation finishes so fast. I introduced the dialog because I thought it was good to have a feedback when performing lengthy file imports, just like dropping hundreds of files into the playlist with auto-cue enabled.
In the German forum, other people have reported strange errors related to BASS.DLL, only ocurring in v.43 but not in the previous snapshot. This misterious auto-cue bug might also be related to BASS.DLL. In between snapshot 484 and v.43, I have changed the way in which several internal components are initialized, including the interface to BASS.DLL. However, these changes are not relevant for version 2.1 (but only for v3.0, which I have started to prepare - more details to follow). I will undo a these changes and prepare a new snapshot based on .v42-484, plus the bug fixes since then (yes, Cad, also stop logging). Let's see if that helps.