Hi @wassermann,

C:\Users\Administrator\IBM\RFT\customization\ won't work; the external JARs need to go in the RFT customization directory contained within %ALLUSERSPROFILE%.

This folder is normally "hidden" so it is not visible in Windows Explorer by default (maybe that's why you couldn't find it)? If in doubt, just open "Start > Run", paste the following, and click OK:
%ALLUSERSPROFILE%\IBM\RFT\customization\

Also note that the literal path does vary by version of Windows, and that although the above information reflects the default location you can hardcode any path you want my modifying a RFT registry key. See my post here for more details:
http://www.ibm.com/developerworks/forums/thread.jspa?threadID=401778

To avoid this error when invoking RFT script playback via the RFT CLI (command-line interface), you need to put a copy of all the external JARs used by your script in the folder that is set in this registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Rational Software\Rational Test\8\Rational FT Customization Directory

The default value set by the installer is:

%ALLUSERSPROFILE%\IBM\RFT\customization[/code:1:613d353bf9]

Which on Windows 7 is here: 

C:\ProgramData\IBM\RFT\customization[/code:1:613d353bf9] and on Windows XP is here:

C:\Documents and Settings\All Users\IBM\RFT\customization[/code:1:613d353bf9]

Cheers,
Patrick