Thanks for the input SurferTim
I did another test today , and i more an more confused.
here is what i did :
1) load the ASCII table example program without the ethernet shield
=> Everything ok , upload and the serial output listed all the ascii code
2) install the shield and reload the ascii table example program
=> still OK
note that when the ethernet cable is connected the both link and 100M led are blinking
3) load my program for the ethernet shield (with the shield still connected)
=> upload was success full but at the of the upload the link and 100M led from the ethernet shied stop blinking
=> but the program (a simply took this example http://arduino.cc/en/Tutorial/WebServer
) did not run , serial console empty , and nothing on the internet browser
And after this no more able to load any other program without getting the stk500v2_ReceiveMessage(): timeout error message
Only way to come back is to unplug the shield and re program.
Seem there is a conflict between the serial and the ethereal shield ? look like the serial port is loss as soon as a program is using the ethernet shield ?
Note i did this test with 2 different ethernet shield R3 and R2 and both are failing , and on an other side both shield are working well with the same program, on a ardunio UNO rev2
If someone have some idea i would appreciate