just droping the exception quickly before moving on to testing:

System.Data.SqlClient.SqlException: CREATE UNIQUE INDEX terminated because a duplicate key was found for index ID 3. Most significant primary key is 'œuvre'.
Could not create constraint. See previous errors.
The statement has been terminated.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async)
at System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe)
at System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at DotNetNuke.Data.SqlDataProvider.ExecuteADOScript(String SQL)
at DotNetNuke.Data.SqlDataProvider.ExecuteScript(String Script, Boolean UseTransactions)


if not exists (select * from dbo.sysobjects where id = object_id(N'IX_DNN_SearchWord'))
ALTER TABLE dbo.DNN_SearchWord ADD CONSTRAINT
IX_DNN_SearchWord UNIQUE NONCLUSTERED (Word) ON [PRIMARY]

seems there were duplicate search words for some reason, so a small update to the upgrade scripts to trim the table may prevent the failure.

cheers

clean your search tables following these instructions and rerun the sql statement

if not exists (select * from dbo.sysobjects where id = object_id(N'IX_DNN_SearchWord')) 
ALTER TABLE dbo.DNN_SearchWord ADD CONSTRAINT 
IX_DNN_SearchWord UNIQUE NONCLUSTERED (Word) ON [PRIMARY] 

as a script from inside the textbox in Host :: SQL menu item