problem whit creating fragments files

Dear Sir: i'm working whit examples (pentane in this case) and when i tried to generate fragments files i getting the following error:

*********Cassandra setup*********

Cassandra location: /home/vani/Documents/programas/Cassandra_V1.1/Src/cassandra_gfortran_openMP.exe
Scanning input file...
Number of species found: 1
The MCF file number 1 is: pentane.mcf
Species 1 has 3 fragments


Creating input MCF generation file for species 1...
Done...
Running Cassandra to generate MCF files...
Done...
Traceback (most recent call last):
File "/home/vani/Documents/programas/Cassandra_V1.1/Scripts/Frag_Library_Setup/library_setup.py", line 540, in <module>
"_1.mcf",'r')
IOError: [Errno 2] No such file or directory: 'species1/fragments/frag_1_1.mcf'



How to solve this?
Regards, vanina.