Turboreg does not recognize the images

[koji]

Hi everyone,

I am a fairly new ImageJ user and I am having trouble with inconsistency when trying to run Turboreg plugin.
All I want to do is run the plugin.
But for some reason, it worked a few times but then suddenly started not working a few hours later.
When I try to run the plugin, now I get an error message "At least two grey scale or RGB stack images are required".
This is what I did.
File > Import > Image sequence (20 tiff RGB files of 500 kb each)
Plugins > Turboreg

As for trouble shooting, I tried the following;
1. Accompanying plugin Stackreg (Interestingly, this plugin seems to always recognize the files!)
2.  Changed image type by Image > Type > RGB stack (and reverting back to RGB or changing to all other image types)
3. Opened each image separately and converted them to a stack using Image > Stacks > Images to stack
4. Different file format such as jpg, bmp.
5. Uninstall and re-install ImageJ or Turboreg/restart computer etc.
6. Used another Windows 7 (home edition) computer (my computer is Windows 7 Enterprise) and attempted the plugin.
7. Installed Ubuntu platform and downloaded ImageJ/Turboreg
8. Tried Turboreg with Fiji.

I am probably stupid and missing something really important.
But I do not know what.
I tried interpreting the script for the error message but my programming knowledge was too poor to understand.
Any advice would be greatly appreciated!
 (note, I can not understand programming much, sorry!)

Many thanks in advance,

koji