CvH - thnx also for replying. And yes, tried it with two different versions (1.4.8 and 2.9p (portable)), also tried Win32DiskImager (under Win10 and another time under Win7 (just in case Win10 was the problem), aswell as with DD from a Linux Shell...
PS: See the Ubuntu Bug #458482 (an old bug from 2009) describes the problem that I am facing... Bug #458482 “usb drives imaged with usb-creator fail to boot on ...” : Bugs : usb-creator package : Ubuntu
PSS: Problem solved... For those with the same issue here is the fix:
1. Boot into Linux (Live or installed)
2. open a terminal (CLI, shell, bash, etc. whatever you fancy and call it)...
3. enter the following:
sudo dd if=/dev/sdX1 of=/media/sda1/usb-stick.img bs=4M
sudo dd of=/dev/sdX if=/media/sda1/usb-stick.img bs=4M
sudo rm /media/sda1/usb-stick.img
source: Live-USB › Wiki › ubuntuusers.de
change the sdX part to reflect the mount point of your USB stick. OF in the first line, pls. change the path to a place/dev/dir with enough storage space to hold the USB stick...
(the above was done using Parted Magic, booted to x64 in RAM, with an empty drive as SDA1)
(what this does, is copy the USB Stick as image to the HDD (or whereever one copies it), then rewrites this image onto the USB stick. Some BIOS's have issues with USB sticks formated as HDDs, and this changes the format more or less to that of a floppy)
(I hope this explanation is clear enough for anyone to understand )
4. reboot and enjoy a functioning install stick...