Hardware Failure or Software fixable

Hi folks,
I've a question with my Uno. Some weeks ago it starts with having timeouts while uploading via onboard ISP. I spend a lot of time finding the cause. With a USBasp everything is fine, except for Sketches writing to console. Without using console the Atmel runs. The Uno stops if a sketch writing debug messages.
Could it be that the Mega Chip is defect, or do I have a fixable Code error?
Thanks, Thomas