diff -w -u -r /tmp/avrdude-5.1/ser_posix.c ./ser_posix.c
--- /tmp/avrdude-5.1/ser_posix.c	2005-08-29 18:30:05.000000000 -0700
+++ ./ser_posix.c	2006-04-03 09:08:25.000000000 -0700
@@ -65,6 +65,9 @@
   { 0,      0 }                 /* Terminator. */
 };
 
+static struct termios original_termios;
+static int saved_original_termios;
+
 static speed_t serial_baud_lookup(long baud)
 {
   struct baud_mapping *map = baud_lookup_table;
@@ -75,7 +78,7 @@
     map++;
   }
 
-  fprintf(stderr, "%s: serial_baud_lookup(): unknown baud rate: %ld", 
+  fprintf(stderr, "%s: serial_baud_lookup(): unknown baud rate: %ld\n", 
           progname, baud);
   exit(1);
 }
@@ -87,33 +90,38 @@
   speed_t speed = serial_baud_lookup (baud);
   
   if (!isatty(fd))
-    return -1;
+    return -ENOTTY;
   
   /*
    * initialize terminal modes
    */
   rc = tcgetattr(fd, &termios);
   if (rc < 0) {
-    fprintf(stderr, "%s: ser_setspeed(): tcgetattr() failed, %s", 
-            progname, strerror(errno));
+    fprintf(stderr, "%s: ser_setspeed(): tcgetattr() failed", 
+            progname);
     return -errno;
   }
 
-  termios.c_iflag = 0;
-  termios.c_oflag = 0;
-  termios.c_cflag = 0;
+  /*
+   * copy termios for ser_close if we haven't already
+   */
+  if (! saved_original_termios++) {
+    original_termios = termios;
+  }
+
+  cfmakeraw(&termios);
+  termios.c_cflag &= ~CSIZE;
   termios.c_cflag |=   (CS8 | CREAD | CLOCAL);
-  termios.c_lflag = 0;
   termios.c_cc[VMIN]  = 1;
   termios.c_cc[VTIME] = 0;
 
   cfsetospeed(&termios, speed);
   cfsetispeed(&termios, speed);
   
-  rc = tcsetattr(fd, TCSANOW, &termios);
+  rc = tcsetattr(fd, TCSANOW | TCSAFLUSH, &termios);
   if (rc < 0) {
-    fprintf(stderr, "%s: ser_setspeed(): tcsetattr() failed, %s", 
-            progname, strerror(errno));
+    fprintf(stderr, "%s: ser_setspeed(): tcsetattr() failed", 
+            progname);
     return -errno;
   }
 
@@ -137,7 +145,7 @@
   /*
    * open the serial port
    */
-  fd = open(port, O_RDWR | O_NOCTTY /*| O_NONBLOCK*/);
+  fd = open(port, O_RDWR | O_NOCTTY | O_NONBLOCK);
   if (fd < 0) {
     fprintf(stderr, "%s: ser_open(): can't open device \"%s\": %s\n",
             progname, port, strerror(errno));
@@ -150,8 +158,8 @@
   rc = ser_setspeed(fd, baud);
   if (rc) {
     fprintf(stderr, 
-            "%s: ser_open(): can't set attributes for device \"%s\"\n",
-            progname, port);
+            "%s: ser_open(): can't set attributes for device \"%s\": %s\n",
+            progname, port, strerror(-rc));
     exit(1);
   }
 
@@ -161,7 +169,18 @@
 
 static void ser_close(int fd)
 {
-  /* FIXME: Should really restore the terminal to original state here. */
+  /*
+   * restore original termios settings from ser_open
+   */
+  if (saved_original_termios) {
+    int rc = tcsetattr(fd, TCSANOW | TCSADRAIN, &original_termios);
+    if (rc) {
+      fprintf(stderr, 
+              "%s: ser_close(): can't reset attributes for device: %s\n",
+              progname, strerror(errno));
+    }
+    saved_original_termios = 0;
+  }
 
   close(fd);
 }
diff -u avrdude-5.1/stk500.c avrdude-5.1-patch/stk500.c
--- avrdude-5.1/stk500.c	2005-08-30 03:30:05.000000000 +0200
+++ avrdude-5.1-patch/stk500.c	2006-04-07 10:26:08.000000000 +0200
@@ -625,13 +625,14 @@
 static int stk500_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m, 
                               int page_size, int n_bytes)
 {
-  unsigned char buf[16];
+  unsigned char buf[page_size + 16];  
   int memtype;
   unsigned int addr;
   int a_div;
   int block_size;
   int tries;
   unsigned int n;
+  unsigned int i;
   int flash;
 
   if (page_size == 0) {
@@ -697,17 +698,19 @@
   retry:
     tries++;
     stk500_loadaddr(pgm, addr/a_div);
-    buf[0] = Cmnd_STK_PROG_PAGE;
-    buf[1] = (block_size >> 8) & 0xff;
-    buf[2] = block_size & 0xff;
-    buf[3] = memtype;
-    stk500_send(pgm, buf, 4);
-
-	stk500_send(pgm, &m->buf[addr], block_size);
-
-    buf[0] = Sync_CRC_EOP;
-    stk500_send(pgm, buf, 1);
-
+    
+    /* build command block and avoid multiple send commands as it leads to a crash
+        of the silabs usb serial driver on mac os x */
+    i = 0;
+    buf[i++] = Cmnd_STK_PROG_PAGE;
+    buf[i++] = (block_size >> 8) & 0xff;
+    buf[i++] = block_size & 0xff;
+    buf[i++] = memtype;
+    memcpy(&buf[i], &m->buf[addr], block_size);
+    i += block_size;
+    buf[i++] = Sync_CRC_EOP;
+    stk500_send( pgm, buf, i);
+    
     stk500_recv(pgm, buf, 1);
     if (buf[0] == Resp_STK_NOSYNC) {
       if (tries > 33) {
diff -u -r1.36 configure.ac
--- avrdude-5.1/Makefile.in     2006-09-26 19:59:27.000000000 +0200
+++ avrdude-5.1-patched/Makefile.in     2006-09-26 19:59:03.000000000 +0200
@@ -100,7 +100,7 @@
        avrdude-stk500v2.$(OBJEXT) avrdude-term.$(OBJEXT) \
        avrdude-usb_libusb.$(OBJEXT)
 avrdude_OBJECTS = $(am_avrdude_OBJECTS)
-avrdude_LDADD = $(LDADD)
+avrdude_LDADD = $(LDADD) -framework CoreFoundation -framework IOKit
 DEFAULT_INCLUDES = -I. -I$(srcdir) -I.
 depcomp = $(SHELL) $(top_srcdir)/depcomp
 am__depfiles_maybe = depfiles