Thanks Jason - I've commented out the line as suggested and all seems to work fine.
Just a point to note though: I downloaded the fix and copied the files as per the read me file:
C:\Documents and Settings\<Your User Name>\Application Data\Adobe\Dreamweaver CS4\en_US\Configuration\shared\WebAssist\ApplicationBuilder\Helpers\library.php"
before I started this. Have just re-copied the files and the problem still exists!
For now I'll have to remember to comment out the rogue line but would appreciate your thoughts.