Updated SERIAL define to MYSERIAL, because Arduino 1.0 defines SERIAL as 0.

Marlin/Marlin.h

 #include "WString.h"
 
 #if MOTHERBOARD == 8  // Teensylu
-  #define SERIAL Serial
+  #define MYSERIAL Serial
 #else
-  #define SERIAL MSerial
+  #define MYSERIAL MSerial
 #endif
 
 //this is a unfinsihed attemp to removes a lot of warning messages, see:
 //#define MYPGM(s)  (__extension__({static prog_char __c[]  = (s); &__c[0];})) //this does not work but hides the warnings
 
 
-#define SERIAL_PROTOCOL(x) SERIAL.print(x);
+#define SERIAL_PROTOCOL(x) MYSERIAL.print(x);
 #define SERIAL_PROTOCOLPGM(x) serialprintPGM(MYPGM(x));
-#define SERIAL_PROTOCOLLN(x) {SERIAL.print(x);SERIAL.write('\n');}
-#define SERIAL_PROTOCOLLNPGM(x) {serialprintPGM(MYPGM(x));SERIAL.write('\n');}
+#define SERIAL_PROTOCOLLN(x) {MYSERIAL.print(x);MYSERIAL.write('\n');}
+#define SERIAL_PROTOCOLLNPGM(x) {serialprintPGM(MYPGM(x));MYSERIAL.write('\n');}
 
 
 const char errormagic[] PROGMEM ="Error:";
   char ch=pgm_read_byte(str);
   while(ch)
   {
-    SERIAL.write(ch);
+    MYSERIAL.write(ch);
     ch=pgm_read_byte(++str);
   }
 }

Marlin/Marlin.pde

 void setup()
 { 
   setup_powerhold();
-  SERIAL.begin(BAUDRATE);
+  MYSERIAL.begin(BAUDRATE);
   SERIAL_PROTOCOLLNPGM("start");
   SERIAL_ECHO_START;
   SERIAL_ECHOPGM("Marlin: ");
 
 void get_command() 
 { 
-  while( SERIAL.available() > 0  && buflen < BUFSIZE) {
-    serial_char = SERIAL.read();
+  while( MYSERIAL.available() > 0  && buflen < BUFSIZE) {
+    serial_char = MYSERIAL.read();
     if(serial_char == '\n' || serial_char == '\r' || serial_char == ':' || serial_count >= (MAX_CMD_SIZE - 1) ) 
     {
       if(!serial_count) return; //if empty line
 void FlushSerialRequestResend()
 {
   //char cmdbuffer[bufindr][100]="Resend:";
-  SERIAL.flush();
+  MYSERIAL.flush();
   SERIAL_PROTOCOLPGM("Resend:");
   SERIAL_PROTOCOLLN(gcode_LastN + 1);
   ClearToSend();

Marlin/SdBaseFile.cpp

       && DIR_IS_FILE_OR_SUBDIR(&dir)) break;
   }
   // indent for dir level
-  for (uint8_t i = 0; i < indent; i++) SERIAL.write(' ');
+  for (uint8_t i = 0; i < indent; i++) MYSERIAL.write(' ');
 
   // print name
   for (uint8_t i = 0; i < 11; i++) {
     if (dir.name[i] == ' ')continue;
     if (i == 8) {
-      SERIAL.write('.');
+      MYSERIAL.write('.');
       w++;
     }
-    SERIAL.write(dir.name[i]);
+    MYSERIAL.write(dir.name[i]);
     w++;
   }
   if (DIR_IS_SUBDIR(&dir)) {
-    SERIAL.write('/');
+    MYSERIAL.write('/');
     w++;
   }
   if (flags & (LS_DATE | LS_SIZE)) {
-    while (w++ < 14) SERIAL.write(' ');
+    while (w++ < 14) MYSERIAL.write(' ');
   }
   // print modify date/time if requested
   if (flags & LS_DATE) {
-    SERIAL.write(' ');
+    MYSERIAL.write(' ');
     printFatDate( dir.lastWriteDate);
-    SERIAL.write(' ');
+    MYSERIAL.write(' ');
     printFatTime( dir.lastWriteTime);
   }
   // print size if requested
   if (!DIR_IS_SUBDIR(&dir) && (flags & LS_SIZE)) {
-    SERIAL.write(' ');
-    SERIAL.print(dir.fileSize);
+    MYSERIAL.write(' ');
+    MYSERIAL.print(dir.fileSize);
   }
-  SERIAL.println();
+  MYSERIAL.println();
   return DIR_IS_FILE(&dir) ? 1 : 2;
 }
 //------------------------------------------------------------------------------
   for (uint8_t i = 0; i < 11; i++) {
     if (dir.name[i] == ' ')continue;
     if (i == 8) {
-      SERIAL.write('.');
+      MYSERIAL.write('.');
       w++;
     }
-    SERIAL.write(dir.name[i]);
+    MYSERIAL.write(dir.name[i]);
     w++;
   }
   if (DIR_IS_SUBDIR(&dir) && printSlash) {
-    SERIAL.write('/');
+    MYSERIAL.write('/');
     w++;
   }
   while (w < width) {
-    SERIAL.write(' ');
+    MYSERIAL.write(' ');
     w++;
   }
 }
 //------------------------------------------------------------------------------
 // print uint8_t with width 2
 static void print2u( uint8_t v) {
-  if (v < 10) SERIAL.write('0');
-  SERIAL.print(v, DEC);
+  if (v < 10) MYSERIAL.write('0');
+  MYSERIAL.print(v, DEC);
 }
 //------------------------------------------------------------------------------
 /** %Print a directory date field to Serial.
  * \param[in] fatDate The date field from a directory entry.
  */
 void SdBaseFile::printFatDate(uint16_t fatDate) {
-  SERIAL.print(FAT_YEAR(fatDate));
-  SERIAL.write('-');
+  MYSERIAL.print(FAT_YEAR(fatDate));
+  MYSERIAL.write('-');
   print2u( FAT_MONTH(fatDate));
-  SERIAL.write('-');
+  MYSERIAL.write('-');
   print2u( FAT_DAY(fatDate));
 }
 
  */
 void SdBaseFile::printFatTime( uint16_t fatTime) {
   print2u( FAT_HOUR(fatTime));
-  SERIAL.write(':');
+  MYSERIAL.write(':');
   print2u( FAT_MINUTE(fatTime));
-  SERIAL.write(':');
+  MYSERIAL.write(':');
   print2u( FAT_SECOND(fatTime));
 }
 //------------------------------------------------------------------------------
 bool SdBaseFile::printName() {
   char name[13];
   if (!getFilename(name)) return false;
-  SERIAL.print(name);
+  MYSERIAL.print(name);
   return true;
 }
 //------------------------------------------------------------------------------

Marlin/SdFatUtil.cpp

  * \param[in] str Pointer to string stored in flash memory.
  */
 void SdFatUtil::print_P( PGM_P str) {
-  for (uint8_t c; (c = pgm_read_byte(str)); str++) SERIAL.write(c);
+  for (uint8_t c; (c = pgm_read_byte(str)); str++) MYSERIAL.write(c);
 }
 //------------------------------------------------------------------------------
 /** %Print a string in flash memory followed by a CR/LF.
  */
 void SdFatUtil::println_P( PGM_P str) {
   print_P( str);
-  SERIAL.println();
+  MYSERIAL.println();
 }
 //------------------------------------------------------------------------------
 /** %Print a string in flash memory to Serial.

Marlin/stepper.cpp

     timer = (unsigned short)pgm_read_word_near(table_address);
     timer -= (((unsigned short)pgm_read_word_near(table_address+2) * (unsigned char)(step_rate & 0x0007))>>3);
   }
-  if(timer < 100) { timer = 100; SERIAL.print("Steprate to high : "); SERIAL.println(step_rate); }//(20kHz this should never happen)
+  if(timer < 100) { timer = 100; MYSERIAL.print("Steprate to high : "); MYSERIAL.println(step_rate); }//(20kHz this should never happen)
   return timer;
 }