Pro micro not communicating

Other Hardware 3rd Party Boards
1

Recently i bought a pro micro 5v 16 MHz (benselectronics.nl).

At first it didnt show a serial port but that is fixed. Now it wont communicate at all.
Simple digital hardware like a led works fine, but when it comes to an lcd or an bluetooth module it just doesnt communicate.

I tried the I2C scanner sketch from the arduino playground to find an adress for the lcd, but it just hangs after "scanning..." (the lcd works just fine on the uno).

The leds on the board are constantly on.

Another problem i have is that my mac (el captain) crashes sometimes when plugging in the pro micro or when it is connected.

I hope someone got a solution.
Thanks in advance.

2

Did you try the loop back test?

Try a second Arduino to see if this one is trashed.

3

No i will try
Thanks.

4

i've tried but without succes. The test did work on my uno, but not on my pro micro.
i've tried two cables (not "only-power" cables) and i'm sure i picked the right serial port.
on the internet they say you need to download the driver, but the pro micro doesn't have one (i think).

now what?...

Does somebody has an idea how to fix this?

thanks in advance.