System.OverflowException was unhandled
  Message=Conversion overflows.
  Source=System.Data
  StackTrace:
       at System.Data.SqlTypes.SqlDecimal.ToDecimal()
       at Xtensive.Sql.SqlServer.v09.TypeMapper.ReadDecimal(DbDataReader reader, Int32 index) in c:\Projects\dataobjects.net\Xtensive.Sql\Xtensive.Sql\Drivers\SqlServer\v09\TypeMapper.cs:line 114
       at Xtensive.Sql.TypeMapping.ReadValue(DbDataReader reader, Int32 index) in c:\Projects\dataobjects.net\Xtensive.Sql\Xtensive.Sql\ValueTypeMapping\TypeMapping.cs:line 26
       at Xtensive.Storage.Providers.Sql.DbDataReaderAccessor.Read(DbDataReader source, Tuple target) in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Providers\Sql\DbDataReaderAccessor.cs:line 26
       at Xtensive.Storage.Providers.Sql.CommandProcessor.<RunTupleReader>d__0.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Providers\Sql\CommandProcessing\CommandProcessor.cs:line 131
       at Xtensive.Storage.Providers.Sql.SessionHandler.<Xtensive.Storage.Providers.Sql.IQueryExecutor.ExecuteTupleReader>d__a.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Providers\Sql\SessionHandler.IQueryExecutor.cs:line 25
       at Xtensive.Storage.Providers.Sql.SqlProvider.<OnEnumerate>d__0.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Providers\Sql\SqlProvider.cs:line 62
       at Xtensive.Storage.Rse.Providers.ExecutableProvider.<GetEnumerator>d__0.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Rse\Providers\ExecutableProvider.cs:line 220
       at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
       at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
       at Xtensive.Storage.Rse.RecordSet.<GetGreedyEnumerator>d__0.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Orm\Xtensive.Orm\Storage\Rse\RecordSet.cs:line 43
       at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
       at Xtensive.Core.EnumerableExtensions.<Batch>d__20`1.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Core\Xtensive.Core\Core\Extensions\EnumerableExtensions.cs:line 499
       at Xtensive.Core.EnumerableExtensions.<ApplyBeforeAndAfter>d__28`1.MoveNext() in c:\Projects\dataobjects.net\Xtensive.Core\Xtensive.Core\Core\Extensions\EnumerableExtensions.cs:line 595
       at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
       at Project26.Program.Main(String[] args) in c:\users\klekovkin\documents\visual studio 2010\Projects\Project26\Project26\Program.cs:line 37
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

How to reproduce:

field:

    [Field(Scale = 8, Precision = 28)]
    public decimal dec { get; set; }

and code to test:

using (var session = domain.OpenSession())
{
    using (var transactionScope = session.OpenTransaction())
    {
        // Creating new persistent object
        var helloWorld = new MyEntity(session) { dec = 123456123456123456.12341234m };
        foreach (var myEntity in session.Query.All<MyEntity>())
            Console.WriteLine(myEntity.dec);
        transactionScope.Complete();
    }
}