I tried to connect to MYSQL:

<domain name="Default" upgradeMode="Recreate" provider="mysql" connectionString="SERVER=localhost;DATABASE=wsrscheduler;UID=wsr;PASSWORD=wsrpwd">

While direct connection works:

var connectionString = "SERVER=localhost;" + "DATABASE=wsrscheduler;UID=wsr;PASSWORD=xxx";
var connection = new MySqlConnection(connectionString);
connection.Open();

Assuming you parse the MYSQL server version with VersionInfo.Parse()? That fails because the version is "5.5.25a" and cannot be parsed because of the 'a'.

System.FormatException was unhandled
  Message=Die Eingabezeichenfolge hat das falsche Format.
  Source=mscorlib
  StackTrace:
       bei System.Version.TryParseComponent(String component, String componentName, VersionResult& result, Int32& parsedComponent)
       bei System.Version.TryParseVersion(String version, VersionResult& result)
       bei System.Version..ctor(String version)
       bei Xtensive.Sql.Drivers.MySql.DriverFactory.CreateDriver(String connectionString, String forcedVersion)
       bei Xtensive.Sql.SqlDriverFactory.CreateDriver(ConnectionInfo connectionInfo, String forcedVersion)
       bei Xtensive.Orm.Providers.Sql.DomainHandler.Initialize()
       bei Xtensive.Orm.Building.Builders.DomainBuilder.CreateHandlers()
       bei Xtensive.Orm.Building.Builders.DomainBuilder.BuildDomain(DomainConfiguration configuration, DomainBuilderConfiguration builderConfiguration)
       bei Xtensive.Orm.Upgrade.UpgradingDomainBuilder.BuildStageDomain(UpgradeStage stage)
       bei Xtensive.Orm.Upgrade.UpgradingDomainBuilder.Build(DomainConfiguration configuration)
       bei Xtensive.Orm.Domain.Build(DomainConfiguration configuration)
       bei WSRServices.DataServiceBase.LoadModules() in D:\Work\WSR\WSRServiceBaseLib\WSRDataServiceBaseLib\DataServiceBase.cs:Zeile 41.
       bei WSRServices.ServiceBase.OnStartup() in D:\Work\WSR\WSRServiceBaseLib\WSRServiceBaseLib\ServiceBase.cs:Zeile 499.
       bei WSRServices.ChildServiceBase.Run() in D:\Work\WSR\WSRServiceBaseLib\WSRServiceBaseLib\ChildServiceBase.cs:Zeile 51.
       bei WSRServices.ServiceBase.Start() in D:\Work\WSR\WSRServiceBaseLib\WSRServiceBaseLib\ServiceBase.cs:Zeile 341.
       bei WSRServices.Scheduler.Program.Main(String[] args) in D:\Work\WSR\WSRServices\WSRSchedulerService\Program.cs:Zeile 26.
       bei System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       bei Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       bei System.Threading.ThreadHelper.ThreadStart()
  InnerException: