--- trunk/OOPSE/libmdtools/DumpReader.cpp	2004/06/07 14:26:33	1252
+++ trunk/OOPSE/libmdtools/DumpReader.cpp	2004/06/11 17:16:21	1268
@@ -611,6 +611,12 @@ char* DumpReader::parseDumpLine(char* readLine, StuntD
     // check that the quaternion vector is normalized
 
     qSqr = (q[0] * q[0]) + (q[1] * q[1]) + (q[2] * q[2]) + (q[3] * q[3]);
+
+    if (fabs(qSqr) < 1e-6) {
+      sprintf(painCave.errMsg,
+          "initial quaternion error (q0^2 + q1^2 + q2^2 + q3^2 ~ 0).\n");
+       return strdup(painCave.errMsg);
+    }
 
     qLength = sqrt( qSqr );
     q[0] = q[0] / qLength;