There is an error in the automatic comport detection for airmail in nx0.5(august). This error can be fixed easily. Just open a terminal window by pressing ctrl+alt+t at the same time. Next get root access by entering 
sudo su and then copy and past the following code into the terminal window:
Code:
cat >/usr/local/bin/comports << EOF
#!/bin/bash
# script to link the non static /dev/ttyUSB[N] ports
# to static /dev/com[N]. configuration will be saved
# to a configuration file which is unique for each
# computer
exec 2>/dev/null
if [ ! "\$USER" = "root" ]; then
  sudo \$0 \$1 \$2 \$3 \$4 \$5 \$6 \$7 \$8 \$9
  exit
fi
product=\$(dmidecode -t 2|grep -i Product)
product=\${product#*: }
product=\$(echo \$product | sed -e 's/[^A-Za-z0-9.]//g' | tr '[a-z]' '[A-Z]')
product=\${product:0:8}
serial=\$(dmidecode -t 2|grep -i Serial)
serial=\${serial#*: }
serial=\$(echo \$serial | sed -e 's/[^A-Za-z0-9]//g' | tr '[a-z]' '[A-Z]')
serial=\${serial:0:8}
comcfg=/etc/comports{\$product.\$serial}.conf
if [ \$1 = "-d" ]; then
  rm -f \$comcfg
fi
if [ \$1 = "-s" ]; then
  rm -f \$comcfg
  find /dev/serial/by-path/*|sort|while read line
  do
    echo \$line >>\$comcfg
  done
fi
rm -f /dev/com*
ln -s /dev/ttyS0 /dev/com1
echo /dev/com1 \-\> /dev/ttyS0
ln -s /dev/ttyS1 /dev/com2
echo /dev/com2 \-\> /dev/ttyS1
port=3
if [ -e \$comcfg ]; then
  cat \$comcfg|while read line
  do
    if [ -e \$line ]; then
      ln -s \$line /dev/com\$port
      echo -n "/dev/com\$port -> /dev/"
      ls -lisa \$line|awk -F '/' '{print \$7}'
    else
      echo "/dev/com\$port -> *** not available ***"
    fi
    let port=port+1
  done
  echo com port configuration from {\$product.\$serial}
else
  find /dev/serial/by-path/*|sort|while read line
  do
    ln -s \$line /dev/com\$port
    echo -n "/dev/com\$port -> /dev/"
    ls -lisa \$line|awk -F '/' '{print \$7}'
    let port=port+1
  done
fi
for line in \$(ls /dev/rfcomm*); do
  ln -s \$line /dev/com\$port
  echo /dev/com\$port \-\> \$line
  let port=port+1
done
if [ \$1 = "-s" ]; then
  echo "new com port configuration has been saved"
fi
if [ \$1 = "-d" ]; then
  echo "com port configuration for this computer has been deleted"
fi
EOF
If you have a harddisk install the changes will be permanent. If you run from usb stick make sure you have a memory with persistency created (can be done in the bootmenu when you start from the usb)
Next you have to connect and turn on your pactor modem and 
afterwards start airmail. Configure your comports and radio settings and thats it. Should work now without trouble.