Please provide the following information if you want to report a bug:

1) Please state the SPM and Marsbar version you are using, the OS (Linux or Windows) and if you are working with 3D or 4D NIfTI files.
2) What did you intend to do?
3) Paste the error message from Matlab.
4) Provide the data (from one subject) and the analysis configuration script to reproduce the bug.

I will try to find a solution as fast as possible.