I use the ATtiny13V uC
I don't use th MKII emulator
I set the PORTB5 (RESET, AIN0, DebuWire, I/O pin) as digital input without using the internal Pull-Up.
The problem is that when I connect a voltmeter or an osciloscope to this pin I always read Vcc voltage.
I did it at any other pins but not the same (everything works fine)
I have make the same using 5 pices of tiny 13 but always the same problem.
Something else: when I use a small external Pull-down 100Ω connected at PORTB5 the Voltage remains Vcc. I think that this means that the pin is unexpected digital Output.
Note that I have set this pin as digital pin (not Analog) and I have set this pin as I/O pin (not Reset pin)