import from G1 1.3 to G2 2.1.2 fails

Gallery version = 2.1.2 core 1.1.0.2
PHP version = 4.3.10-16 apache
Webserver = Apache/1.3.33
Database = mysql 4.0.24_Debian-10sarge2-log, lock.system=flock
Toolkits = ArchiveUpload, Exif, Getid3, NetPBM, SquareThumb, Thumbnail
Acceleration = none, none
Operating system = Linux wintermute 2.6.8-2-686 #1 Tue Aug 16 13:22:48 UTC 2005 i686
Default theme = matrix
Locale = en_US
Browser = Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.7) Gecko/20060909 Firefox/1.5.0.7

The problem occurs while trying to import an old G1 (v1.3) installation. I suspect it is related to the fact that import procedure doesn't detect any users in G1 installation - says "No available users" (while logging into admin account on G1 shows 4 users including admin). I am able to select the albums and encoding (old encoding is KOI8-R and conversion works, as the confirmation page shows correct album names), but when import starts, it shows a fully painted progress bar for Importing users BUT no "continue" button.

Please advise.

Many thanks in advance for any useful information.