Hi, This is more or less that I was thinking after look carefully all the errors. Thank you for your answer and your time. Melchor S. -- View this message in context: http://gromacs.5086.x6.nabble.com/Problem-with-Amber99SB-ILDN-ff-tp5009641p5010029.html Sent from the GROMACS Users Forum mailing list archive at Nabble.com.