avrdude: initialization failed, custom board

Hi there!

I designed a custom board with an atmega8 (smd) on it with a 16Mhz crystal and programmed via a 6 pin ICSP header. I soldered everything and loaded a program directly from the arduino ide to the board via the sparkfun USBtiny programmer on it. It worked from the beginning without a problem. The board basically has two MOSFETs on it to flash some LEDs and this worked perfectly.
I noticed that the programm is way too slow (about 10x slower, delay(1000) lasted about 10s). I thought that maybe some fuses have to be set to use the external crystal an thought I'd try to upload the bootloader, maybe this helps. While trying this, I got the error

avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

Since then, I can't upload anything, no bootloader and no program.

Did I fry the chip? Is there anything to do about it?