Here is another issue partially related to my .
I just changed default serial port speed from 19200 to 9600 and clicked OK. Tera Term opened serial port connection. I saved configuration in default TERATERM.INI file. Now, while the first Tera Term instance is still running, I need to start a second copy to establish SSH connection to a remote host. Instead of New Connection window, "Cannot open port" error message pops up.
Just to make it clear - both these posts are not about the errors that cause application failure, but about user experience. There are certain things user expects and things that s/he does not. Starting an application and seeing right away an error message is definitely not expected.