diff -Naur lammps-18Dec07/src/CLASS2/improper_class2.cpp lammps-19Dec07/src/CLASS2/improper_class2.cpp
--- lammps-18Dec07/src/CLASS2/improper_class2.cpp	2007-12-06 17:11:14.000000000 -0700
+++ lammps-19Dec07/src/CLASS2/improper_class2.cpp	2007-12-19 10:20:01.000000000 -0700
@@ -477,7 +477,7 @@
 
     if (evflag)
       ev_tally(i1,i2,i3,i4,nlocal,newton_bond,eimproper,
-	       fabcd[i1],fabcd[i3],fabcd[i4],
+	       fabcd[0],fabcd[2],fabcd[3],
 	       delr[0][0],delr[0][1],delr[0][2],
 	       delr[1][0],delr[1][1],delr[1][2],
 	       delr[2][0]-delr[1][0],delr[2][1]-delr[1][1],
@@ -821,7 +821,7 @@
 
     if (evflag)
       ev_tally(i1,i2,i3,i4,nlocal,newton_bond,eimproper,
-	       fabcd[i1],fabcd[i3],fabcd[i4],
+	       fabcd[0],fabcd[2],fabcd[3],
 	       delxAB,delyAB,delzAB,delxBC,delyBC,delzBC,delxBD,delyBD,delzBD);
   }
 }
diff -Naur lammps-18Dec07/src/MOLECULE/atom_vec_molecular.cpp lammps-19Dec07/src/MOLECULE/atom_vec_molecular.cpp
--- lammps-18Dec07/src/MOLECULE/atom_vec_molecular.cpp	2007-10-04 11:57:04.000000000 -0600
+++ lammps-19Dec07/src/MOLECULE/atom_vec_molecular.cpp	2007-12-19 10:19:53.000000000 -0700
@@ -344,8 +344,8 @@
 
 int AtomVecMolecular::pack_border_one(int i, double *buf)
 {
-  buf[1] = molecule[i];
-  return 2;
+  buf[0] = molecule[i];
+  return 1;
 }
 
 /* ---------------------------------------------------------------------- */
@@ -372,8 +372,8 @@
 
 int AtomVecMolecular::unpack_border_one(int i, double *buf)
 {
-  molecule[i] = static_cast<int> (buf[1]);
-  return 2;
+  molecule[i] = static_cast<int> (buf[0]);
+  return 1;
 }
 
 /* ----------------------------------------------------------------------
diff -Naur lammps-18Dec07/src/read_data.cpp lammps-19Dec07/src/read_data.cpp
--- lammps-18Dec07/src/read_data.cpp	2007-06-22 10:59:17.000000000 -0600
+++ lammps-19Dec07/src/read_data.cpp	2007-12-19 10:20:18.000000000 -0700
@@ -940,36 +940,96 @@
     else if (strcmp(keyword,"Atoms") == 0) skip_lines(natoms);
     else if (strcmp(keyword,"Velocities") == 0) skip_lines(natoms);
 
-    else if (strcmp(keyword,"Pair Coeffs") == 0) skip_lines(atom->ntypes);
-    else if (strcmp(keyword,"Bond Coeffs") == 0) 
+    else if (strcmp(keyword,"Pair Coeffs") == 0) {
+      if (force->pair == NULL) 
+	error->all("Must define pair_style before Pair Coeffs");
+      skip_lines(atom->ntypes);
+
+    } else if (strcmp(keyword,"Bond Coeffs") == 0) {
+      if (atom->avec->bonds_allow == 0) 
+	error->all("Invalid data file section: Bond Coeffs");
+      if (force->bond == NULL) 
+	error->all("Must define bond_style before Bond Coeffs");
       skip_lines(atom->nbondtypes);
-    else if (strcmp(keyword,"Angle Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"Angle Coeffs") == 0) {
+      if (atom->avec->angles_allow == 0) 
+	error->all("Invalid data file section: Angle Coeffs");
+      if (force->angle == NULL) 
+	error->all("Must define angle_style before Angle Coeffs");
       skip_lines(atom->nangletypes);
-    else if (strcmp(keyword,"Dihedral Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"Dihedral Coeffs") == 0) {
       skip_lines(atom->ndihedraltypes);
-    else if (strcmp(keyword,"Improper Coeffs") == 0) 
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: Dihedral Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before Dihedral Coeffs");
+
+    }  else if (strcmp(keyword,"Improper Coeffs") == 0) {
+      if (atom->avec->impropers_allow == 0) 
+	error->all("Invalid data file section: Improper Coeffs");
+      if (force->improper == NULL) 
+	error->all("Must define improper_style before Improper Coeffs");
       skip_lines(atom->nimpropertypes);
 
-    else if (strcmp(keyword,"BondBond Coeffs") == 0) 
+    } else if (strcmp(keyword,"BondBond Coeffs") == 0) {
+      if (atom->avec->angles_allow == 0) 
+	error->all("Invalid data file section: BondBond Coeffs");
+      if (force->angle == NULL) 
+	error->all("Must define angle_style before BondBond Coeffs");
       skip_lines(atom->nangletypes);
-    else if (strcmp(keyword,"BondAngle Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"BondAngle Coeffs") == 0) {
+      if (atom->avec->angles_allow == 0) 
+	error->all("Invalid data file section: BondAngle Coeffs");
+      if (force->angle == NULL) 
+	error->all("Must define angle_style before BondAngle Coeffs");
       skip_lines(atom->nangletypes);
 
-    else if (strcmp(keyword,"MiddleBondTorsion Coeffs") == 0) 
+    } else if (strcmp(keyword,"MiddleBondTorsion Coeffs") == 0) {
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: MiddleBondTorsion Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before MiddleBondTorsion Coeffs");
       skip_lines(atom->ndihedraltypes);
-    else if (strcmp(keyword,"EndBondTorsion Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"EndBondTorsion Coeffs") == 0) {
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: EndBondTorsion Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before EndBondTorsion Coeffs");
       skip_lines(atom->ndihedraltypes);
-    else if (strcmp(keyword,"AngleTorsion Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"AngleTorsion Coeffs") == 0) {
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: AngleTorsion Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before AngleTorsion Coeffs");
       skip_lines(atom->ndihedraltypes);
-    else if (strcmp(keyword,"AngleAngleTorsion Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"AngleAngleTorsion Coeffs") == 0) {
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: AngleAngleTorsion Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before AngleAngleTorsion Coeffs");
       skip_lines(atom->ndihedraltypes);
-    else if (strcmp(keyword,"BondBond13 Coeffs") == 0) 
+
+    } else if (strcmp(keyword,"BondBond13 Coeffs") == 0) {
+      if (atom->avec->dihedrals_allow == 0) 
+	error->all("Invalid data file section: BondBond13 Coeffs");
+      if (force->dihedral == NULL) 
+	error->all("Must define dihedral_style before BondBond13 Coeffs");
       skip_lines(atom->ndihedraltypes);
 
-    else if (strcmp(keyword,"AngleAngle Coeffs") == 0) 
+    } else if (strcmp(keyword,"AngleAngle Coeffs") == 0) {
+      if (atom->avec->impropers_allow == 0) 
+	error->all("Invalid data file section: AngleAngle Coeffs");
+      if (force->improper == NULL) 
+	error->all("Must define improper_style before AngleAngle Coeffs");
       skip_lines(atom->nimpropertypes);
 
-    else if (strcmp(keyword,"Bonds") == 0) {
+    } else if (strcmp(keyword,"Bonds") == 0) {
 
       for (i = 1; i < cmax; i++) count[i] = 0;
       if (force->newton_bond)