Just recently, Our Search function has stopped working entirely. Both Advanced Search and Key Word Search Box no longer return any results.

Also noticing a new recurring Error message in the Event Log:

Error:
System.Web A potentially dangerous Request.Form value was detected from the client (ctl00$MainContentHolder$ContentColumnControl3$ctl00$KeywordField="...t lesbian <a href="http://www....").[ at System.Web.HttpRequest.ValidateString(String s, String valueName, String collectionName) at System.Web.HttpRequest.ValidateNameValueCollection(NameValueCollection nvc, String collectionName) at System.Web.HttpRequest.get_Form() at System.Web.HttpRequest.get_HasForm() at System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) at System.Web.UI.Page.DeterminePostBackMode() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at System.Web.UI.Page.ProcessRequest(HttpContext context) at ASP.bvmodules_producttemplates_johnprodtemplate_product_aspx.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) ]

Any Ideas ?

Hosting with Applied-I
VS-1 Plan
BVC 5.3.1

You get this error when script tags or html tags are part of your search. This is standard ASP.Net security measure to avoid script injection attacks. You can disable this for a specific page (in this case search.aspx) by adding the RequestValidation="False" tag to the page directive on your aspx file (the first line). This is a fix. But you should look into why thats happening in the first place. Did you change any search related stuff?