> All this happened with 3.31 under Windows 98SE.

The 3.31 release has many problems, especially with file 
structures and parsing, so the result might be better with 
3.32

> Another not so nice fact is that under Windows the log
> file can not be read while the transfer is running.

Just click on the menu "Log" / "View log"

> It also seems there is no error-log created when the
> transfer is cancelled by the user.

If the interruption is too fast, yet, there might be no log 
att all. But else, the logfile should at least exists (hts-
log.txt)