Once upon a time I had this problem. I know of three ways to fix it, two of which high_flyer mentioned above. They are:

  1. LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/qextserialport.so.1/ (somewhat frowned upon - see how-to referenced below)
  2. cp qextserialpport.so.1 /executable/directory/
  3. as root - add "/path/to/qextserialport.so.1/" to ld.so.conf and run ldconfig (man ldconfig & man ld.so)


Here is a good read on shared libraries FYI.