Image not found

I'm using OruxMapsDesktop 2.0.20beta to convert maps I downloaded from www.cnig.es. These tif-maps come with a .tfw file.
example of a .twf:
2.5
0.0
0.0
-2.5
600932.500000
4188352.500000

When selecting the calibration .twf file in OruxMapsDesktop the Image File textbox is filled with the correct image name and path but still a dialog message pops up with the notice: "An error occurred while reading calibration file:Image not found".

The image tif-file is in the same directory as the .twf file.

What can be wrong?

I converted the image from tiff to png and now it works.
I had installed jai_imageio-1_1-lib-windows-i586.exe but OruxMapsDesktop doesn't seem to use it.
Any ideas why?

You can also select the tiff file manually.

Steed,
Yes that's true but then it doesn't read the calibration file.
And I have no paper version of the maps to read the 4 corner coordinates to calibrate.
But anyway thanks for the suggestion.

some program doesn't support tiff files, so you need to convert tiff to png vb.net. then you won't get the erro while you are maping tiff.