sorry it took so long to get back to this but family concerns often take up my time....anyway, here is what I have done although I use Ubuntu.
In GIMP I go to the Movie Menu and choose "Mplayer based extraction"

that's because at least on my system the "Extract videorange" doesn't work. I get the same load error messages you got.
this brings up this window:

add your video file from the 1st field.
you will have to calculate how many frames there are in your video if you wish all your frames rendered. If your video is 2 minutes long and it's 25 frames per second that's 1500 frames.
choose your file name and the location of your rendered files.
then choose the format: I prefer png if I will be doing processing in another program.