"Has no one got an idea?

The only remedy I see is changing the Attiny45. Do I need a boatloader afterwards?"

"Hi!
A friend of mine gave me ohne of his boards (he had two). Unfortunately it was one of the boards with the incorrect code and the wrong fuses. I fixed the problem with ponyprog2000.
What I did was to disable the CKDIV8 and load the…"