That happens when the StrokesPlus certificate is not installed. I have some instructions somewhere in the forum, but running the regular setup exe will install the certificate as well. The portable zip has the cert file included as well, but I don't remember the exact steps to install
Ok i see [url=http://www.strokesplus.com/forum/topic/1110/help-portable-s-x64-cannot-longer-be-launched]this[/url] and [url=http://www.strokesplus.com/forum/topic/565/experimental-sign-strokesplus-for-win-8-interop]this[/url].