i try to upload program to arduino but i can't .. the LED L is blinking rather rapidly - 5 times a second or more HELP ME PLEASE!
and when i reset arduino... don't happen something .. continue blinking 
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
sry for my english!
It's difficult to diagnose this without more information. Like your whole set-up.
For some reason, it sounds like your board is not responding. Have you tried another USB cable?
I have had that message after unplugging and re-plugging the Arduino while the IDE serial monitor is open. Try un-plugging &restarting the IDE. Seems the OS assigns a new COM port for the board and the IDE sticks with the old one ( can't reselect in menu either ).
I'm running windows 7 so this may be irrelevant to you.
Are you using the Arduino Software 1.0?
Try it with an older one.
There is a bug see
Do you have anywhere in your code "!!!". See http://arduino.cc/forum/index.php/topic,101375.0.html