In the CMS, I go to Members, open the search node and search for * (wildcard) and I get the yellow screen of death:

Server Error in '/' Application.
Object reference not set to an instance of an object.Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 

[NullReferenceException: Object reference not set to an instance of an object.]
   Lucene.Net.Search.BooleanQuery.Rewrite(IndexReader reader) +312
   Lucene.Net.Search.BooleanQuery.Rewrite(IndexReader reader) +116
   Lucene.Net.Search.IndexSearcher.Rewrite(Query original) +24
   Lucene.Net.Search.Query.Weight(Searcher searcher) +24
   Lucene.Net.Search.Searcher.CreateWeight(Query query) +11
   Lucene.Net.Search.Searcher.Search(Query query, Filter filter, Int32 n, Sort sort) +15
   Examine.LuceneEngine.SearchResults.DoSearch(Query query, IEnumerable`1 sortField) +85
   Examine.LuceneEngine.SearchResults..ctor(Query query, IEnumerable`1 sortField, IndexSearcher searcher) +82
   Examine.LuceneEngine.Providers.LuceneSearcher.Search(ISearchCriteria searchParams) +104
   Examine.LuceneEngine.Providers.LuceneSearcher.Search(String searchText, Boolean useWildcards) +225
   umbraco.presentation.umbraco.members.MemberSearch.ButtonSearch_Click(Object sender, EventArgs e) +424
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563