I cannot diagnose anything without a log ! Please, follow the
rules of this forum.
The only advice I can give you is to uninstall the Cool VL Viewer (using its provided uninstaller: it will take care of the registry keys), delete the user settings files (for Windows XP, they are in: C:\Documents and Settings\your_login_name_here\Application Data\SecondLife\user_settings\ ), manually delete the Cool VL Viewer cache directory (for Windows XP it is C:\Documents and Settings\your_login_name_here\Local Settings\Application Data\CoolVLViewer), and then reinstall the viewer.