Fixed crashes.

Marlin/Marlin.pde

 #include "Marlin.h"
 #include "speed_lookuptable.h"
 
-char version_string[] = "0.9.9";
+char version_string[] = "0.9.10";
 
 #ifdef SDSUPPORT
 #include "SdFat.h"
 // implements the reverse pass.
 void planner_reverse_pass() {
   char block_index = block_buffer_head;
-  block_t *block[3] = {
-    NULL, NULL, NULL  };
-  while(block_index != block_buffer_tail) {    
+  block_index--;
+  block_t *block[3] = { NULL, NULL, NULL };
+  while(block_index != block_buffer_tail) {  
+    block_index--;
+    if(block_index < 0) block_index = BLOCK_BUFFER_SIZE-1;  
     block[2]= block[1];
     block[1]= block[0];
     block[0] = &block_buffer[block_index];
     planner_reverse_pass_kernel(block[0], block[1], block[2]);
-    block_index--;
-    if(block_index < 0) {
-      block_index = BLOCK_BUFFER_SIZE-1;
-    }
   }
-//  planner_reverse_pass_kernel(NULL, block[0], block[1]);
+  planner_reverse_pass_kernel(NULL, block[0], block[1]);
 }
 
 // The kernel called by planner_recalculate() when scanning the plan from first to last entry.
 // mm. Microseconds specify how many microseconds the move should take to perform. To aid acceleration
 // calculation the caller must also provide the physical length of the line in millimeters.
 void plan_buffer_line(float x, float y, float z, float e, float feed_rate) {
-
   // The target position of the tool in absolute steps
   // Calculate target position in absolute steps
   long target[4];
   // Compute the acceleration rate for the trapezoid generator. 
   float travel_per_step = block->millimeters/block->step_event_count;
   if(block->steps_x == 0 && block->steps_y == 0 && block->steps_z == 0) {
-    block->acceleration = ceil( (retract_acceleration)/travel_per_step); // convert to: acceleration steps/sec^2
+    block->acceleration_st = ceil( (retract_acceleration)/travel_per_step); // convert to: acceleration steps/sec^2
   }
   else {
     block->acceleration_st = ceil( (acceleration)/travel_per_step);      // convert to: acceleration steps/sec^2