pw.x stops with error in reading.

There is an error in the input data. Usually it is a misspelled namelist variable, or an empty input file. Note that out-of-bound indices in dimensioned variables read in the namelist may cause the code to crash with really mysterious error messages. Also note that input data files containing ^M (Control-M) characters at the end of lines (typically, files coming from Windows PC) may yield error in reading. If none of the above applies and the code stops at the first namelist (``control'') and you are running in parallel: your MPI libraries might not be properly configured to allow input redirection, so that what you are effectively reading is an empty file. See section ``Running on parallel machines'', or inquire with your local computer wizard (if any).