diff -U5 -r src/tfio.c src/tfio.c
--- src/tfio.c	2007-01-13 18:12:39.000000000 -0500
+++ src/tfio.c	2007-02-02 16:50:12.000000000 -0500
@@ -495,10 +495,11 @@
     const char *q, *sval;
     char *specptr, quote;
     const conString *Sval;
     int len, min, max, leftjust, stars;
     attr_t attrs = buf->attrs;
+    va_list aq;
 
     if (!(flags & SP_APPEND) && buf->data) Stringtrunc(buf, 0);
     while (*fmt) {
         if (*fmt != '%' || *++fmt == '%') {
             for (q = fmt + 1; *q && *q != '%'; q++);
@@ -520,11 +521,13 @@
         switch (*fmt) {
         case 'd': case 'i':
         case 'x': case 'X': case 'u': case 'o':
         case 'f': case 'e': case 'E': case 'g': case 'G':
         case 'p':
-            vsprintf(tempbuf, spec, ap);
+            va_copy(aq, ap);
+            vsprintf(tempbuf, spec, aq);
+            va_end(aq);
             Stringcat(buf, tempbuf);
             /* eat the arguments used by vsprintf() */
             while (stars--) (void)va_arg(ap, int);
             switch (*fmt) {
             case 'd': case 'i':