I get the same message, no difference weather I choose Slack 9.1, 10.0 or 10.1. I'm using Slackware 10.2, and kde 3.5 from: 
ftp://ftp.kde.org/pub/kde/stable/3.5/contrib/Slackware/10.2/
When I compile knetworkconf from source it works fine (when I choose Slackware 10.1 from menu).
I tried to change slackware 10.1 to slackware 10.2 in files from directory:/opt/kde/share/apps/knetworkconf/backends, but no luck.

SVN commit 492393 by jbaptiste:

BUG: 113799 Changed some error messages to be more descriptive. I Hope it's enough.

 M  +1 -1      knetworkconf.cpp  
 M  +18 -18    knetworkconfigparser.cpp  


--- branches/KDE/3.5/kdeadmin/knetworkconf/knetworkconf/knetworkconf.cpp #492392:492393
@@ -63,7 +63,7 @@
   if (netInfo == NULL)
   {
     KMessageBox::error(this,
-                        i18n("Could not load network info."),
+                        i18n("Could not load network configuration information."),
                         i18n("Error Reading Configuration File"));
     //kapp->quit();
     //exit(1);
--- branches/KDE/3.5/kdeadmin/knetworkconf/knetworkconf/knetworkconfigparser.cpp #492392:492393
@@ -38,8 +38,8 @@
   if (pathToProgram.isEmpty())
   {
     KMessageBox::error(0,
-                        i18n("Could not find the network detection scripts. Something is wrong with your installation.\n Please check that  \n{KDE_PATH}/%1 \nfile is present.").arg(BACKEND_PATH),
-                        i18n("Could Not Find Network Backend Script"));
+                        i18n("Could not find the backend script for the network configuration detection. Something is wrong with your installation.\n Please check that  \n{KDE_PATH}/%1 \nfile is present.").arg(BACKEND_PATH),
+                        i18n("Could Not Find Network Configuration Backend Script"));
       dialog->close();
       exit(5);
       //kapp->quit();
@@ -63,8 +63,8 @@
     {
     // error handling
       KMessageBox::error(0,
-                        i18n("Could not execute network detection scripts. Something is wrong with your installation."),
-                        i18n("Could Not Launch Network Backend Script"));
+                        i18n("Could not execute backend script for the network configuration detection. Something is wrong with your installation."),
+                        i18n("Could Not Launch Network Configuration Backend Script"));
       dialog->close();
       exit(5);
     }
@@ -93,9 +93,9 @@
  if ( !procDetect->start() )
   {
 // error handling
-    KMessageBox::error(0,
-                        i18n("Could not execute network detection scripts. Something is wrong with your installation."),
-                        i18n("Could Not Launch Network Backend Script"));
+      KMessageBox::error(0,
+                        i18n("Could not execute backend script for the network configuration detection. Something is wrong with your installation."),
+                        i18n("Could Not Launch Network Configuration Backend Script"));
     exit(5);
   }
 }
@@ -113,7 +113,7 @@
     if ( !doc.setContent( xmlOuput.utf8(),false,&err,&x,&y  ) )
     {
       KMessageBox::error(0,
-                      i18n("Could not parse the XML file."),
+                      i18n("Could not parse the XML output from the network configuration backend."),
                       i18n("Error While Listing Network Interfaces"));
 //        qDebug("error: %s %d,%d",err.latin1(),x,y);
     }
@@ -302,9 +302,9 @@
    
   if ( !procSaveNetworkInfo->start() )
   {
-    KMessageBox::error(0,
-                        i18n("Could not execute network saving scripts. Something is wrong with your installation."),
-                        i18n("Could Not Launch Network Backend Script"));
+      KMessageBox::error(0,
+                        i18n("Could not execute backend script for the network configuration detection. Something is wrong with your installation."),
+                        i18n("Could Not Launch Network Configuration Backend Script"));
   }
 
   procSaveNetworkInfo->writeToStdin(xml);
@@ -822,8 +822,8 @@
     if ( !doc.setContent( xmlOuput.utf8(),false,&err,&x,&y  ) )
     {
       KMessageBox::error(0,
-                      i18n("Could not parse the XML file."),
-                      i18n("Error"));
+                      i18n("Could not parse the XML output from the network configuration backend."),
+                      i18n("Error Loading The Network Configuration"));
 //        qDebug("error: %s %d,%d",err.latin1(),x,y);
     }
       
@@ -1000,9 +1000,9 @@
  	if ( !procDetect->start() )
   {
 // error handling
-    KMessageBox::error(0,
-                        i18n("Could not list supported platforms. Something is wrong with your installation."),
-                        i18n("Could Not Launch Network Backend Script"));
+      KMessageBox::error(0,
+                        i18n("Could not execute backend script for the network configuration detection. Something is wrong with your installation."),
+                        i18n("Could Not Launch Network Configuration Backend Script"));
     exit(5);
 	}
 
@@ -1016,8 +1016,8 @@
   if ( !doc.setContent( xmlOuput.utf8() ) )
   {
     KMessageBox::error(0,
-                         i18n("Could not parse the XML file of supported platforms."),
-                         i18n("Error"));
+                         i18n("Could not parse the list of supported platforms from the network configuration backend."),
+                         i18n("Error Obtaining Supported Platforms List"));
   }
   QDomElement root = doc.documentElement();
   QDomNode node = root.firstChild();