Mihai,

Here is my 2 cents worth.

I made one programmer before couple years for AT89C2051.
It wouldn’t work. I spent a lot of time and finally I converted hex code into binary and found that for some reason code was shifted for one byte down.
I added one line a code at the start of program (move r7, A), compiled, converted hex to bin, and first line was removed with bin editor. I saved new binary file, converted to hex and put into MCU and processor started work.

What I want to tell you?
Write simple code, fill up your microcontroller, try to read and check that you have what you put into MCU.

Thanks,

Goran