Arduino BT upload problem
To be able to bootload code on the Arduino, the programmer must attempt to connect within about 3 seconds of the AVR coming out of reset.  I the ArduinoBT I have lacks a connection that the traditional USB versions have, which allows the programming software to reset the Arduino by itself.  In lieu of that, you must physically hit the button to do it yourself.


  I cannot see how can I press the reset button on the Arduino during the upload when I have to type the PIN in a different window.


You should only have to type the Bluetooth passkey once, so after the BT module is paired with your computer, the computer should be able to freely connect, so long as it is powered.

The Bluetooth module and AVR are very separate; you can hold the AVR in reset, and the Bluetooth module will happily run along.  If you're cutting power to the entire board to reset it, it may indeed be difficult to have the BT module come online, connect to it, and initiate programming all within 3 seconds.