Just started with a fresh new Umbraco 6.1.6 from NuGet, Setup the database with SQL Compact, and installed Workflow 2.2 and ran into this issue as soon as it loaded up. Looks like you don't support SQL Compact:

http://cl.ly/image/0n133Z1j0D3p

[ArgumentException: Keyword not supported: 'flush interval'.]

   System.Data.Common.DbConnectionOptions.ParseInternal(Hashtable parsetable, String connectionString, Boolean buildChain, Hashtable synonyms, Boolean firstKey) +5371672

   System.Data.Common.DbConnectionOptions..ctor(String connectionString, Hashtable synonyms, Boolean useOdbcRules) +95

   System.Data.SqlClient.SqlConnectionString..ctor(String connectionString) +59

   System.Data.SqlClient.SqlConnectionFactory.CreateConnectionOptions(String connectionString, DbConnectionOptions previous) +24

   System.Data.ProviderBase.DbConnectionFactory.GetConnectionPoolGroup(DbConnectionPoolKey key, DbConnectionPoolGroupOptions poolOptions, DbConnectionOptions& userConnectionOptions) +167

   System.Data.SqlClient.SqlConnection.ConnectionString_Set(DbConnectionPoolKey key) +61

   System.Data.SqlClient.SqlConnection.set_ConnectionString(String value) +66

   System.Data.SqlClient.SqlConnection..ctor(String connectionString, SqlCredential credential) +26

   System.Data.SqlClient.SqlConnection..ctor(String connectionString) +6

   FergusonMoriyam.Workflow.Infrastructure.DatabaseHelper.SqlServerDatabaseHelper.PrepareConnection() +42

   FergusonMoriyam.Workflow.Infrastructure.DatabaseHelper.SqlServerDatabaseHelper.CreateCommand(String text) +17

   FergusonMoriyam.Workflow.Infrastructure.WorkflowInstantiationCriteriaRepository.List() +29

   FergusonMoriyam.Workflow.Application.WorkflowInstantiationCriteriaService.List() +11

   FergusonMoriyam.Workflow.Application.EventService.RegisterEvents() +73

   FergusonMoriyam.Workflow.Umbraco.Application.SpringApplicationEventListener.HandleApplicationEvent(Object sender, ApplicationEventArgs e) +84