Ok i found a solution.
Go to C:\Program Files\Microsoft Dynamics CRM\CRMWeb\_grid\cmds
Modify dlg_queueitemroute.aspx (Create a backup before modifying CRM Files)
Replace <input type="radio" class="radio" id="rdExistingUser" name="rdUserOptions" value="0" runat="server" onclick="userOptionRadioClick(new Sys.UI.DomEvent(event))"/>
By <input type="radio" class="radio" id="rdExistingUser" name="rdUserOptions" checked value="1" runat="server" onclick="userOptionRadioClick(new Sys.UI.DomEvent(event))"/>
And Replace <input type="radio" class="radio" id="rdSelectedUser" name="rdUserOptions" checked value="1" runat="server" onclick="userOptionRadioClick(new Sys.UI.DomEvent(event))"/>
By <input type="radio" class="radio" id="rdSelectedUser" name="rdUserOptions" value="0" runat="server" onclick="userOptionRadioClick(new Sys.UI.DomEvent(event))"/>