In your screen shot i see you have installed Photo Assist and Ebay Store Builder, These 2 have been discontinued for about 3 or 4 years and will not wirk in CS 5, they should be uninstalled.
I see you also have CSS Form Builder 2 and HTML Editor 3, when installing these 2 together, you should make sure to install the CSS Form Builder 2.0.1 Support Release 2 version from the Download center, make sure to install CSS Form Builder first, then install HTML Editor 3.
Also, Cookies toolkit is not built into Security Assist 2, It should not be installed if you are also installing Security Assist 2.
what i would do is to recreate your workspace layout (Window -> Workspace Layouts -> Reset '<your layout name>'), close Dreamweaver, then delete the cache file:
common_installation_issues.pdf
Now open the extension manager and uninstall the following extensions:
Photo Assist
Ebay Store Builder
Cookies Toolkit
Form Builder
HTML Editor
Security Assist
Go to the Download center and make sure to download the CSS Form Builder 2.0.1 Support Release 2 version.
The install CSS Form Builder, followed by HTML Editor 3 and finally Security Assist 2.
