diff --git a/src/atom.cpp b/src/atom.cpp
index 9303fdafd6..0ea5128302 100644
--- a/src/atom.cpp
+++ b/src/atom.cpp
@@ -53,7 +53,8 @@ Atom::Atom(LAMMPS *lmp) : Pointers(lmp)
   extra_bond_per_atom = 0;
 
   firstgroupname = NULL;
-  sortfreq = 1000;
+  sortfreq = 0;
+  //sortfreq = 1000;
   userbinsize = 0.0;
   maxbin = maxnext = 0;
   binhead = NULL;
@@ -353,13 +354,15 @@ void Atom::modify_params(int narg, char **arg)
       iarg += 2;
     } else if (strcmp(arg[iarg],"first") == 0) {
       if (iarg+2 > narg) error->all("Illegal atom_modify command");
-      if (strcmp(arg[iarg+1],"all") == 0) delete [] firstgroupname;
-      else {
+      if (strcmp(arg[iarg+1],"all") == 0) {
+	delete [] firstgroupname;
+	firstgroupname = NULL;
+      } else {
 	int n = strlen(arg[iarg+1]) + 1;
 	firstgroupname = new char[n];
 	strcpy(firstgroupname,arg[iarg+1]);
+	sortfreq = 0;
       }
-      sortfreq = 0;
       iarg += 2;
     } else if (strcmp(arg[iarg],"sort") == 0) {
       if (iarg+3 > narg) error->all("Illegal atom_modify command");
@@ -1360,9 +1363,9 @@ void Atom::sort()
   for (i = 0; i < nbins; i++) binhead[i] = -1;
 
   for (i = nlocal-1; i >= 0; i--) {
-    ix = static_cast<int> ((x[i][0]-bboxlo[0])*bininv);
-    iy = static_cast<int> ((x[i][1]-bboxlo[1])*bininv);
-    iz = static_cast<int> ((x[i][2]-bboxlo[2])*bininv);
+    ix = static_cast<int> ((x[i][0]-bboxlo[0])*bininvx);
+    iy = static_cast<int> ((x[i][1]-bboxlo[1])*bininvy);
+    iz = static_cast<int> ((x[i][2]-bboxlo[2])*bininvz);
     ix = MAX(ix,0);
     iy = MAX(iy,0);
     iz = MAX(iz,0);
@@ -1439,7 +1442,7 @@ void Atom::setup_sort_bins()
   else binsize = 0.5 * neighbor->cutneighmax;
   if (binsize == 0.0) error->all("Atom sorting has bin size = 0.0");
 
-  bininv = 1.0/binsize;
+  double bininv = 1.0/binsize;
 
   // nbin xyz = local bins
   // bbox lo/hi = bounding box of my sub-domain
@@ -1458,10 +1461,15 @@ void Atom::setup_sort_bins()
   nbinx = static_cast<int> ((bboxhi[0]-bboxlo[0]) * bininv);
   nbiny = static_cast<int> ((bboxhi[1]-bboxlo[1]) * bininv);
   nbinz = static_cast<int> ((bboxhi[2]-bboxlo[2]) * bininv);
+  if (domain->dimension == 2) nbinz = 1;
   
-  nbinx = MAX(nbinx,1);
-  nbinx = MAX(nbiny,1);
-  nbinx = MAX(nbinz,1);
+  if (nbinx == 0) nbinx = 1;
+  if (nbiny == 0) nbiny = 1;
+  if (nbinz == 0) nbinz = 1;
+
+  bininvx = nbinx / (bboxhi[0]-bboxlo[0]);
+  bininvy = nbiny / (bboxhi[1]-bboxlo[1]);
+  bininvz = nbinz / (bboxhi[2]-bboxlo[2]);
 
   if (1.0*nbinx*nbiny*nbinz > INT_MAX) 
     error->one("Too many atom sorting bins");
diff --git a/src/atom.h b/src/atom.h
index f54dd89041..39f567f883 100644
--- a/src/atom.h
+++ b/src/atom.h
@@ -203,8 +203,8 @@ class Atom : protected Pointers {
   int *binhead;                   // 1st atom in each bin
   int *next;                      // next atom in bin
   int *permute;                   // permutation vector
-  double userbinsize;             // sorting bin size
-  double bininv;
+  double userbinsize;             // requested sort bin size
+  double bininvx,bininvy,bininvz; // inverse actual bin sizes
   double bboxlo[3],bboxhi[3];     // bounding box of my sub-domain
 
   int memlength;                  // allocated size of memstr
diff --git a/src/universe.cpp b/src/universe.cpp
index 2a432c7250..007c10e11c 100644
--- a/src/universe.cpp
+++ b/src/universe.cpp
@@ -26,7 +26,7 @@ using namespace LAMMPS_NS;
 
 Universe::Universe(LAMMPS *lmp, MPI_Comm communicator) : Pointers(lmp)
 {
-  version = (char *) "7 Jul 2009";
+  version = (char *) "15 Jan 2010";
 
   uworld = communicator;
   MPI_Comm_rank(uworld,&me);