Failed to load module for FS type 'bdb'

After quick Googling it appeared that from branch 1.6.x, TortoiseSVN doesn’t support local file:/// repositories based on BDB and they need to be converted to new FSFS format using ’svnadmin’ command line tool as it is explained in SVNBook. As ’svnadmin’ tool is not present in TortoiseSVN, some additional work is needed.

Finally I did in following way:

1. download and  Tigris build of SVN (it was svn-win32-1.6.1.zip in my case). I’ve tried both 1.5.x and 1.6.x version of CollabNet’s SVN but apparently they do not support local BDB as well,
2. unpack it to any directory, and using command line enter to the bin subdirectory where the svnadmin.exe tool is stored
3. as written in the book, make dump of your repository with following command:

svnadmin dump c:\FullPathToOldRepository > dumpfile.bin

4. create new repository in choosen directory, you can use TorotoiseSVN for it as well, now it won’t ask you for data storage format as BDB is disabled, so it will use FSFS.
5. import dump data into new repository:

svnadmin load c:\FullPathToNewRepository < dumpfile.bin

That is, it worked for me like a charm.