Open multiple files in one editor session failed

[H.A.v.d.Woude]

operating system Win XP sp 3
on a daul core Intel processor

I often use many files for editing at the same time in one editor session( Textpad 5.3.1 from Helois Softwae solutions) .
In the editor is the option 'Allow multiple instances to run' set to NO.
When I open a selection of files the editor runs more than one time with a varying number of files opened. Quite annoying when one has to do the same changes for each opened session.
I don't meet this problem when I use Explorer or WS-FTP 95 LE

[H.A.v.d.Woude]

Print screen of the result opening multiple files

[Tim Kosse]

FileZilla simply executes the associated program and according to the screenshot FileZilla does it quite well. Instead, this is a problem with your editor, it fails to properly communicate with itself.