It seems you are currently running Test Studio version 2011.1.712. This can be verified on the Help tab in the lower left corner of the Standalone version or under "Help > About Microsoft Visual Studio" in our VS plugin.
We included support for Safari 5.1 in a later version, so please download our latest internal build, version 2011.1.825. This is available for download on the "Your Account" page on www.telerik.com
under the Internal Builds Downloads section. Here
is a direct link.
the Telerik team