Hi,
Like I said earlier, I've got no experience with I2C but as far as I understand both signal pins must be digital outputs. I think that it should work on pins with open drain output (ie, pins which can only switch to GND). Pins that are input only won't work as far as I understand.

So, any two pins which can function as digital outputs should work. Make sure any analog functions on these two pins are disabled. If you need help, tell us which chip it is and post the code.

/Henrik.