Can't upload sketch on ATMEGA1280 :(

Hello everyone,
I just unpacked my brand new first ArduinoMega, installed the drivers, set the COM port to COM 7 (which is the correct one) set the Tools>Board to Arduino Mega, opened Examples>Digital>Blink, changed the value of OFF and ON to 100ms, uploaded to Arduino and it worked fine, then i wired the display according to LiquidCrystal>HelloWorld and tried to upload and got an error:

avrdude: stk500_getsync(): not in sync: resp=0x00

avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

Then read troubleshooting, serched this forum and lot of people seem to get this error, so I changed setting s to get verbose data and this is waht i get:

Binary sketch size: 1426 bytes (of a 126976 byte maximum)
C:\Documents and Settings\odolejsi\Plocha\WRK\arduino-0018\hardware/tools/avr/bin/avrdude -CC:\Documents and Settings\odolejsi\Plocha\WRK\arduino-0018\hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega1280 -cstk500v1 -P\\.\COM7 -b9600 -D -Uflash:w:C:\DOCUME~1\odolejsi\LOCALS~1\Temp\build2992731219439880512.tmp\Blink.cpp.hex:i 


avrdude: Version 5.4-arduino, compiled on Oct 11 2007 at 19:12:32
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/

         System wide configuration file is "C:\Documents and Settings\odolejsi\Plocha\WRK\arduino-0018\hardware/tools/avr/etc/avrdude.conf"

         Using Port            : \\.\COM7
         Using Programmer      : stk500v1
         Overriding Baud Rate  : 9600
avrdude: ser_open(): setting dtr
avrdude: Send: 0 [30]   [20] 
avrdude: Send: 0 [30]   [20] 
avrdude: Send: 0 [30]   [20] 
avrdude: Recv: 
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: Send: Q [51]   [20] 
avrdude: Recv: 
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

avrdude done.  Thank you.

Another thing you should probably know is that the program (faster blink) I upladed still seems to work, LED 13 is symetrically and quickly flashing.

When I press reset button flashing stops, after i release the reset button L13 flashes once for about 100ms then it is of for abouta second and then it starts flashing quickly again.

When I pull the USB cable out, L13 and RX and TX flash couple times and then Tx,RX goes off and L13 keeps flashing.

When sending program to Arduino first the L13 keeps flashing then it flashes randomly for a split second then a very short Rx flash and another very short Rx flash, then L13 starts flashing again for couple seconds after that the Rx flashes shortly again and from then on its just L13 flashing again.

Hope this is enough info for someone to be able to help me

PS: It really hurts, I was waiting for it for 3 weeks, now it came, AND IT WORKED and second try its fu*ked

Oh! And it is a laptop with two USB ports (tried both) running Win XP probably SP3. And i changed baudRate in settings.txt in Documents and Settings/Arduino to 9600 just in case, becaues the port in windows is set to 9600

When I pull the USB cable out, L13 and RX and TX flash couple times and then Tx,RX goes off and L13 keeps flashing.

How does L13 keep flashing with no power? Are you powering the Arduino while the USB cable was connected?

My bad, when i pull it out and then plug back in. Only poering by USB, have 9V adapter though so I could try that, too but it hink there is a IC on the board that automatically switches power between USB and adaptor.

I just tried another laptop this time with windows 7 on it and still have the exactly the same problem.

Is there any way to upload the bootloader to Arduino on the board? This laptop has hardware parallel and serial port if it helps.