resolution of ROI images

Dear Romain Valabregue and List,

I have a simple question: I'd like to create an ROI with a 1x1x1 mm resolution. 

I have tried following Romain's suggestion ("You can change it with the option 
(edit option) and 'choose base space for roi' just choose a volume with a 1x1x1 
resolution"; 
http://article.gmane.org/gmane.comp.graphics.spm.marsbar/588/match=resolution).

That is, I selected a normalized structural T1 (nifti) image of one of my 
subjects. But somehow marsbar / spm do not recognize this image "Unknown file 
format"), and now marsbar crashes whenever I want to start it (see error 
below). 

How can I create images with an alternative resolution than 2x2x2, and how can 
I get marsbar up and running again?

Thanks a lot for your help! 

Greetings, Rick 

MarsBaR analysis functions prepended to path
??? Error using ==> spm_vol>subfunc
/home/action/richel/Rick/data/fMRI/p01/structural/crop: Unknown file format.

Error in ==> spm_vol>subfunc1 at 83
    v = subfunc(P(i,:));

Error in ==> spm_vol>subfunc2 at 71
	V = subfunc1(P);