cannot load

Hello,

after a few hours of hard work I started to be unable to load my code (ide 1.6.5 usb connection)

here is the setup
programmer set to avr isp
loaded code "blink"

if i cycle the power once and click sketch upload - it loads consistently as many times as i want
If i cycle the power once and press shift control U - upload never ends
if i dont cycle the power i have: Problem uploading to board. See... with either methods

Exactly the same behaviour with 2 mega and one uno board

Could someone please help me out?
Thanks

If you do shift ctrl + u, that is "Upload using Programmer" - it is attempting to use the external programming hardware you have selected. Do you have such hardware connected to your computer, and wired to the ISP programming header? If not, you should not be surprised that Upload with Programmer doesn't work!
My guess is you didn't know that that option required additional hardware to work, and don't have any such hardware - is that correct?

Please enable verbose upload and post the output you get when you get the "problem uploading to board" message (via normal upload button)

No, i have only the computer connected via a usb cable to arduino boards. I always used shift ctrl u and did not know there was restricted to something special cases

Unless I'm mistaken, shift+ctl+U uses the programmer, and since you don't have one connected, it's expected for that to fail.

So once more I say:

Please enable verbose upload and post the output you get when you get the "problem uploading to board" message (upload via normal upload button)

Thanks, ill do it

setup: mega connected to window computer with ide1.6.5, code: "blink", verbore upload, tools->programmer AVR ISP and I am not sure if this is the correct option.
cycling power-> sketch ->upload => done uploading. sketch ->upload => done uploading... forever
cycling power-> shift ctrl u => uploading... never ends. shift ctrl u=>

avrdude: ser_open(): can't open device "\.\COM3": Access is denied.
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
then, after a variable time, the 10 lines
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x03
...
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x03
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
if i do not wait for the 10 lines then next shift ctrl u will make the same complaint. If I do wait for the 10 lines then the next shift ctrl u will results in uploading forever

In all the situation in which shift ctrl u result in uplading forever, if instead I upload using sketch->upload it will upload ok

Now something I am absolutely sure about is that i always used shift ctrl u - I avoid the usage of the mouse as much as I can for the sake of my shoulders