SharePoint 2010 Web Part Error - Exception from HRESULT: 0x80131904

A client of ours recently encountered a problem with a web part I wrote a while back. This web part is an advanced search which returns results based on information entered into a text box and the criteria selected from a drop down. This web part has been functional on other customer sites and the error which is now encountered by this one client could not be replicated, even after extensive testing on our development environment. This error only appears when the search column is a lookup field and works as expected on any other field type. I have looked around the web to find a resolution specific to my problem, but the majority of the cases refer to an SQL error of the Content Database being out of space, which I don't believe is the case in my instance.

Below is the full stack trace message we receive. Any help to resolve this problem would be very much appreciated!

Exception from HRESULT: 0x80131904 at Microsoft.SharePoint.SPGlobal.HandleComException(COMException comEx) at Microsoft.SharePoint.Library.SPRequest.GetListItemDataWithCallback2(IListItemSqlClient pSqlClient, String bstrUrl, String bstrListName, String bstrViewName, String bstrViewXml, SAFEARRAYFLAGS fSafeArrayFlags, ISP2DSafeArrayWriter pSACallback, ISPDataCallback pPagingCallback, ISPDataCallback pPagingPrevCallback, ISPDataCallback pFilterLinkCallback, ISPDataCallback pSchemaCallback, ISPDataCallback pRowCountCallback, Boolean& pbMaximalView) at Microsoft.SharePoint.SPListItemCollection.EnsureListItemsData() at Microsoft.SharePoint.SPListItemCollection.GetEnumerator() at Biz_AdvancedListSearch_Module.AdvancedListSearch.AdvancedListSearch.btnSearch_Click(Object sender, ImageClickEventArgs e)

EDIT: The problem only arises when the lookup column uses the "contains" search criteria. I use CAML Queries to retrieve the data and using a console application, I determined that this was definitely possible with a lookup field.

A little old, but I had the same issue today. The comparers are case sensitive. should be . In my case, it was , changed to and it works now!