I can "import readline" just fine on AMD64 ubuntu 8.04 under python3.0,
however on 32-bit ubuntu 8.04 I could not "import readline" for
python3.0. It says 
"import readline
ImportError: No module named readline". I made sure both ubuntu machines
have readline installed correctly, python2.x runs well and can import
readline without any issues.

Did you build Python yourself? If so, can you paste the last lines of
the build process like this:

Failed to find the necessary bits to build these modules:
bsddb185           gdbm               linuxaudiodev   
ossaudiodev        spwd               sunaudiodev     
To find the necessary bits, look in setup.py in detect_modules() for the
module's name.

running build_scripts

I just rebuild it again, it went away. not sure what I did wrong at
first try.

The last few lines during compilation are:
INFO: Can't locate Tcl/Tk libs and/or headers

Failed to find the necessary bits to build these modules:
_dbm               _sqlite3           _tkinter        
To find the necessary bits, look in setup.py in detect_modules() for the
module's name.

Looks like I need install python-sqlite etc.