Do you have a App_Browsers/default.browser file in root web/ folder for Telligent Community? If so, does it have the following lines:
<?xml version='1.0' encoding='utf-8'?>
<browsers>
<browser refID="Default">
<controlAdapters>
<adapter controlType="System.Web.UI.WebControls.HyperLink" adapterType="Telligent.Evolution.Controls.Adapters.HyperLinkAdapter, Telligent.Evolution.Controls" />
<adapter controlType="System.Web.UI.WebControls.Image" adapterType="Telligent.Evolution.Controls.Adapters.ImageAdapter, Telligent.Evolution.Controls" />
<adapter controlType="System.Web.UI.HtmlControls.HtmlForm" adapterType="Telligent.Evolution.Controls.Adapters.FormAdapter, Telligent.Evolution.Controls" />
</controlAdapters>
</browser>
<browser id="W3C_Validator" parentID="default">
<identification>
<userAgent match="^W3C_Validator" />
</identification>
<capabilities>
<capability name="browser" value="W3C Validator" />
<capability name="ecmaScriptVersion" value="1.2" />
<capability name="javascript" value="true" />
<capability name="supportsCss" value="true" />
<capability name="tables" value="true" />
<capability name="tagWriter" value="System.Web.UI.HtmlTextWriter" />
<capability name="w3cdomversion" value="1.0" />
</capabilities>
</browser>
</browsers>