diff --git a/doc/Section_errors.html b/doc/Section_errors.html
index 929bc3d355..46d1206f12 100644
--- a/doc/Section_errors.html
+++ b/doc/Section_errors.html
@@ -2923,9 +2923,20 @@ atoms.
 
 <DT><I>Out of range atoms - cannot compute PPPM</I> 
 
-<DD>One or more atoms are attempting to map their charge to a PPPM grid
-point that is not owned by a processor.  This is usually because
-an atom has moved to far in a single timestep. 
+<P>One or more atoms are attempting to map their charge to a PPPM grid
+point that is not owned by a processor.  This is likely for one of two
+reasons, both of them bad.  First, it may mean that an atom near the
+boundary of a processor's sub-domain has moved more than 1/2 the
+<A HREF = "neighbor.html">neighbor skin distance</A> without neighbor lists being
+rebuilt and atoms being migrated to new processors.  This also means
+you may be missing pairwise interactions that need to be computed.
+The solution is to change the re-neighboring criteria via the
+<A HREF = "neigh_modify">neigh_modify</A> command.
+</P>
+<DD>Second, it may mean that an atom has moved far outside a processor's
+sub-domain or even the entire simulation box.  This indicates bad
+physics, e.g. due to highly overlapping atoms, too large a timestep,
+etc. 
 
 <DT><I>POEMS fix must come before NPT/NPH fix</I> 
 
diff --git a/doc/Section_errors.txt b/doc/Section_errors.txt
index 7001b32344..e83d132546 100644
--- a/doc/Section_errors.txt
+++ b/doc/Section_errors.txt
@@ -2921,8 +2921,19 @@ atoms. :dd
 {Out of range atoms - cannot compute PPPM} :dt
 
 One or more atoms are attempting to map their charge to a PPPM grid
-point that is not owned by a processor.  This is usually because
-an atom has moved to far in a single timestep. :dd
+point that is not owned by a processor.  This is likely for one of two
+reasons, both of them bad.  First, it may mean that an atom near the
+boundary of a processor's sub-domain has moved more than 1/2 the
+"neighbor skin distance"_neighbor.html without neighbor lists being
+rebuilt and atoms being migrated to new processors.  This also means
+you may be missing pairwise interactions that need to be computed.
+The solution is to change the re-neighboring criteria via the
+"neigh_modify"_neigh_modify command.
+
+Second, it may mean that an atom has moved far outside a processor's
+sub-domain or even the entire simulation box.  This indicates bad
+physics, e.g. due to highly overlapping atoms, too large a timestep,
+etc. :dd
 
 {POEMS fix must come before NPT/NPH fix} :dt