Mulberry mail client - spell checking is disabled, although dictionaries files present in working folder

Hello to everybody!

Some days ago I have installed the last version 4.0.9a1. Seems, that the soft 
has not been updated for the last 8 years, that it since 2007, however it is 
still pretty good enough to play with on my Windows 7 machine. 

There are many unique features and interesting commands here, but one 
disadvantage might be fatal, that it spelling check engine does not work. The 
appropriate entry in the menu [Edit] is disabled (displayed in gray color), 
shortcut Ctrl+Alt+L does nothing, misspelled words in drafts composer window 
are not underlined etc. 

My first suggestion was, that dictionaries files are absent, but acually they 
present in the application working folder subfolder [Dictionary].

What might be the cause of the problem? One can see, that it is not really 
possible to use a mail client without spell check engine.

Many thanks in advance!