Are you referring to the Sametime 8 Client, if so the answer is yes. If you get this message you can try the following, uninstall all previous version of Sametime and then try re-installing the Sametime 8 Client, If this does not work re-install Notes preferably 7.0.3 and try the install again. If you have additional problems consult the Lotus Sametime Forum.
If you are referring to Sametime 8 or even 7.5.1 on Domino 7, I would not suggest trying to install it because it is not supported. Refer to this link for more details. Adam Gartenberg’s Blog. Make sure you read the comments section.