Assume we have next files in one directory:
golub[1-2].png golub1.png golub2.png
If we try "Add" these files we would be able to Add golub1.png and golub2.png but won't be able Add golub[1-2].png with message "nothing changed. Files golub1.png and golub2.png already added". So golub[1-2].png always recognized as a pattern even if file with exactly this name exists.
Workaround - use command line 'hg add'.
But even after that if we'll try commit this file via TortoiseHg it will not do anything and produce the same message.