What is the build number of the Dreamweaver version you have installed?
Go to Help -> About Dreamweaver.
Click the about dialog box once to force it to scroll to the end, the Version and build number will be listed here.
The build number should be build 3481 or above. If you have an earlier build, you can try installing the Dreamweaver CS3 update available from Adobe at:
downloads_updaters.html#dw9