diff --git a/clientgui/DlgAdvPreferences.cpp b/clientgui/DlgAdvPreferences.cpp
index 1e25c07d0f..557df79cc6 100644
--- a/clientgui/DlgAdvPreferences.cpp
+++ b/clientgui/DlgAdvPreferences.cpp
@@ -396,7 +396,7 @@ void CDlgAdvPreferences::ReadPreferenceSettings() {
     //special day times
     for(int i=0; i< 7;i++) {
         TIME_SPAN& cpu = prefs.cpu_times.week.days[i];
-        if(cpu.present) {
+        if(cpu.present && (cpu.start_hour != cpu.end_hour)) {
             procDayChks[i]->SetValue(true);
             procDayStartTxts[i]->ChangeValue(DoubleToTimeString(cpu.start_hour));
             procDayStopTxts[i]->ChangeValue(DoubleToTimeString(cpu.end_hour));
@@ -413,7 +413,7 @@ void CDlgAdvPreferences::ReadPreferenceSettings() {
     //special net times
     for(int i=0; i< 7;i++) {
         TIME_SPAN& net = prefs.net_times.week.days[i];
-        if(net.present) {
+        if(net.present && (net.start_hour != net.end_hour)) {
             netDayChks[i]->SetValue(true);
             netDayStartTxts[i]->ChangeValue(DoubleToTimeString(net.start_hour));
             netDayStopTxts[i]->ChangeValue(DoubleToTimeString(net.end_hour));
@@ -668,9 +668,11 @@ void CDlgAdvPreferences::UpdateControlStates() {
 bool CDlgAdvPreferences::ValidateInput() {
     wxString invMsgFloat = _("Invalid number");
     wxString invMsgTime = _("Invalid time, value must be between 0:00 and 24:00, format is HH:MM");
+    wxString invMsgTimeSpan = _("Start time must be different from end time");
     wxString invMsgLimit10 = _("Number must be between 0 and 10");
     wxString invMsgLimit100 = _("Number must be between 0 and 100");
     wxString buffer;
+    double startTime, endTime;
 
     // ######### proc usage page
     buffer = m_txtProcUseProcessors->GetValue();
@@ -819,6 +821,12 @@ bool CDlgAdvPreferences::ValidateInput() {
             ShowErrorMessage(invMsgTime,m_txtProcEveryDayStop);
             return false;
         }
+        startTime = TimeStringToDouble(m_txtProcEveryDayStart->GetValue());
+        endTime = TimeStringToDouble(m_txtProcEveryDayStop->GetValue());
+        if (startTime == endTime) {
+            ShowErrorMessage(invMsgTimeSpan,m_txtProcEveryDayStop);
+            return false;
+        }
     }
     
     //all text ctrls in proc special time textBox
@@ -834,6 +842,12 @@ bool CDlgAdvPreferences::ValidateInput() {
                 ShowErrorMessage(invMsgTime,procDayStopTxts[i]);
                 return false;
             }
+            startTime = TimeStringToDouble(procDayStartTxts[i]->GetValue());
+            endTime = TimeStringToDouble(procDayStopTxts[i]->GetValue());
+            if (startTime == endTime) {
+                ShowErrorMessage(invMsgTimeSpan,procDayStopTxts[i]);
+                return false;
+            }
         }
     }
 
@@ -848,6 +862,12 @@ bool CDlgAdvPreferences::ValidateInput() {
             ShowErrorMessage(invMsgTime,m_txtNetEveryDayStop);
             return false;
         }
+        startTime = TimeStringToDouble(m_txtNetEveryDayStart->GetValue());
+        endTime = TimeStringToDouble(m_txtNetEveryDayStop->GetValue());
+        if (startTime == endTime) {
+            ShowErrorMessage(invMsgTimeSpan,m_txtNetEveryDayStop);
+            return false;
+        }
     }
     
     //all text ctrls in net special time textBox
@@ -863,6 +883,12 @@ bool CDlgAdvPreferences::ValidateInput() {
                 ShowErrorMessage(invMsgTime,netDayStopTxts[i]);
                 return false;
             }
+            startTime = TimeStringToDouble(netDayStartTxts[i]->GetValue());
+            endTime = TimeStringToDouble(netDayStopTxts[i]->GetValue());
+            if (startTime == endTime) {
+                ShowErrorMessage(invMsgTimeSpan,netDayStopTxts[i]);
+                return false;
+            }
         }
     }
     return true;
diff --git a/clientgui/sg_DlgPreferences.cpp b/clientgui/sg_DlgPreferences.cpp
index bfea64be57..61e53118cd 100644
--- a/clientgui/sg_DlgPreferences.cpp
+++ b/clientgui/sg_DlgPreferences.cpp
@@ -750,7 +750,9 @@ bool CPanelPreferences::SavePreferenceSettings() {
 bool CPanelPreferences::ValidateInput() {
     wxString invMsgFloat = _("Invalid number");
     wxString invMsgTime = _("Invalid time, value must be between 0:00 and 24:00, format is HH:MM");
+    wxString invMsgTimeSpan = _("Start time must be different from end time");
     wxString invMsgLimit100 = _("Number must be between 0 and 100");
+    double startTime, endTime;
     wxString buffer;
 
     if(m_txtProcIdleFor->IsEnabled()) {
@@ -772,6 +774,12 @@ bool CPanelPreferences::ValidateInput() {
             ShowErrorMessage(invMsgTime,m_txtProcEveryDayStop);
             return false;
         }
+        startTime = TimeStringToDouble(m_txtProcEveryDayStart->GetValue());
+        endTime = TimeStringToDouble(m_txtProcEveryDayStop->GetValue());
+        if (startTime == endTime) {
+            ShowErrorMessage(invMsgTimeSpan,m_txtProcEveryDayStop);
+            return false;
+        }
     }
     
     buffer = m_txtProcUseCPUTime->GetValue();
@@ -791,6 +799,12 @@ bool CPanelPreferences::ValidateInput() {
             ShowErrorMessage(invMsgTime,m_txtNetEveryDayStop);
             return false;
         }
+        startTime = TimeStringToDouble(m_txtNetEveryDayStart->GetValue());
+        endTime = TimeStringToDouble(m_txtNetEveryDayStop->GetValue());
+        if (startTime == endTime) {
+            ShowErrorMessage(invMsgTimeSpan,m_txtNetEveryDayStop);
+            return false;
+        }
     }
     
     if (m_chkDiskMaxSpace->IsChecked()) {