Index: idle_scan.cc
===================================================================
--- idle_scan.cc	(revision 24749)
+++ idle_scan.cc	(working copy)
@@ -303,6 +303,14 @@
 
   proxy->max_groupsz = (o.max_parallelism)? o.max_parallelism : 100;
   proxy->min_groupsz = (o.min_parallelism)? o.min_parallelism : 4;
+
+  /* Prevent performance values from getting out of whack */
+  if (proxy->min_groupsz > proxy->max_groupsz) {
+    error( "WARNING: Idle scan max_groupsz (%i) would have been below min_groupsz (%i). max_groupsz will be set to %i.",
+        proxy->max_groupsz, proxy->min_groupsz, proxy->min_groupsz );
+    proxy->max_groupsz = proxy->min_groupsz;
+  }
+
   proxy->max_senddelay = 100000;
 
   Strncpy(name, proxyName, sizeof(name));
Index: NmapOps.cc
===================================================================
--- NmapOps.cc	(revision 24749)
+++ NmapOps.cc	(working copy)
@@ -478,10 +478,6 @@
     fatal("Sorry -- IPv6 support is currently only available for TCP, UDP, and SCTP port scans and list scan (-sL).  OS detection, random targets and decoys are also not supported with IPv6.  Further support is under consideration.");
   }
 
-  /* Prevent performance values from getting out of whack */
-  if (min_parallelism > max_parallelism)
-    max_parallelism = min_parallelism;
-
   if(ipoptions && osscan)
     error("WARNING: Ip options are NOT used while OS scanning!");
 
Index: osscan2.cc
===================================================================
--- osscan2.cc	(revision 24749)
+++ osscan2.cc	(working copy)
@@ -3163,7 +3163,13 @@
      at least be affected by -T. */
   perf.low_cwnd = MAX(o.min_parallelism, 1);
   perf.max_cwnd = o.max_parallelism? o.max_parallelism : 300;
-  perf.group_initial_cwnd = box(o.min_parallelism, perf.max_cwnd, 10);
+  /* Prevent performance values from getting out of whack */
+  if (perf.low_cwnd > perf.max_cwnd) {
+    error( "WARNING: OS scan max_cwnd (%i) would have been below low_cwnd (%i). max_cwnd will be set to %i.",
+        perf.max_cwnd, perf.low_cwnd, perf.low_cwnd );
+    perf.max_cwnd = perf.low_cwnd;
+  }
+  perf.group_initial_cwnd = box(perf.low_cwnd, perf.max_cwnd, 10);
   perf.host_initial_cwnd = perf.group_initial_cwnd;
   perf.quick_incr = 1;
   perf.cc_incr = 1;
Index: scan_engine.cc
===================================================================
--- scan_engine.cc	(revision 24749)
+++ scan_engine.cc	(working copy)
@@ -1457,7 +1457,13 @@
      at least be affected by -T. */
   perf->low_cwnd = MAX(o.min_parallelism, 1);
   perf->max_cwnd = o.max_parallelism? o.max_parallelism : 300;
-  perf->group_initial_cwnd = box(o.min_parallelism, perf->max_cwnd, 10);
+  /* Prevent performance values from getting out of whack */
+  if (perf->low_cwnd > perf->max_cwnd) {
+    error( "WARNING: ultra_scan max_cwnd (%i) would have been below low_cwnd (%i). max_cwnd will be set to %i.",
+        perf->max_cwnd, perf->low_cwnd, perf->low_cwnd );
+    perf->max_cwnd = perf->low_cwnd;
+  }
+  perf->group_initial_cwnd = box(perf->low_cwnd, perf->max_cwnd, 10);
   perf->host_initial_cwnd = perf->group_initial_cwnd;
   perf->slow_incr = 1;
   /* The congestion window grows faster with more aggressive timing. */
@@ -5835,6 +5841,13 @@
   if (o.min_parallelism) {
     ss.min_width = o.min_parallelism;
   } else ss.min_width = 1;
+  
+  /* Prevent performance values from getting out of whack */
+  if (ss.min_width > ss.max_width) {
+    error( "WARNING: pos_scan max_width (%i) would have been below min_width (%i). max_width will be set to %i.",
+        ss.max_width, ss.min_width, ss.min_width );
+    ss.max_width = ss.min_width;
+  }
 
   ss.initial_packet_width = box(ss.min_width, ss.max_width, ss.initial_packet_width);
   ss.numqueries_ideal = ss.initial_packet_width;
Index: service_scan.cc
===================================================================
--- service_scan.cc	(revision 24749)
+++ service_scan.cc	(working copy)
@@ -1705,7 +1705,12 @@
   if (o.timing_level == 4) desired_par = 30;
   if (o.timing_level >= 5) desired_par = 40;
   // TODO: Come up with better ways to determine ideal_parallelism
-  ideal_parallelism = box(o.min_parallelism, o.max_parallelism? o.max_parallelism : 100, desired_par);
+  int min_par = o.min_parallelism;
+  int max_par = o.max_parallelism? o.max_parallelism : 100;
+  if ( min_par > max_par ) {
+    max_par = min_par;
+  }
+  ideal_parallelism = box(min_par, max_par, desired_par);
 }
 
 ServiceGroup::~ServiceGroup() {