There is a property called "ActiveTabIndex" - The first tab to show which was set to 2. If you set the ActiveTabIndex=0 it will make the first tab the default. We have changed this in the current version and will be availible in the next release 2.88. In the meantime if you would like to change it yourselft to make the first tab the default do the following:
1. Navigate to \desktopmodules\smith.buynow
2. Open up productdetails.ascx and go to line 195
3. Change the line to the following:
<cc1:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0" CssClass="google" Width="600px" >
4. Save the change
Thanks for reporting the issue!
Scott