Hi Ricardo,
If DSpace is unable to create that directory (or the directory just doesn't exist), then it will throw that error which says:
"[full-directory-path] as defined by key 'org.dspace.app.batchitemimport.work.dir' in dspace.cfg is not a valid directory"
So, the first step to solving this issue is to make sure that directory *exists* on your system, or verify that the Tomcat user has permissions to create this directory (if they do not, then DSpace cannot create this on your behalf).
If that doesn't help, then we may need more information about your setup (especially the version of DSpace you are running). It is possible that you are also encountering a bug in an older release.
Tim