Hello,

I am upgrading a Site from version 4.7.2 to 6.2.5 but in the database upgrading process the following error occurs

2015-12-15 10:45:07,921 [7] INFO  Umbraco.Core.DatabaseContext - [Thread 13] Database configuration failed with the following error and stack trace: Thread was being aborted.
   at System.Collections.Generic.HashSet`1.Initialize(Int32 capacity)
   at System.Collections.Generic.HashSet`1..ctor(IEnumerable`1 collection, IEqualityComparer`1 comparer)
   at Umbraco.Core.ConcurrentHashSet`1.GetThreadSafeClone() in d:\Dev\Umbraco6\src\Umbraco.Core\ConcurrentHashSet.cs:line 152
   at Umbraco.Core.ConcurrentHashSet`1.TryAdd(T item) in d:\Dev\Umbraco6\src\Umbraco.Core\ConcurrentHashSet.cs:line 103
   at Umbraco.Core.Persistence.Caching.RuntimeCacheProvider.Save(Type type, IEntity entity) in d:\Dev\Umbraco6\src\Umbraco.Core\Persistence\Caching\RuntimeCacheProvider.cs:line 140
   at Umbraco.Core.Persistence.Repositories.RepositoryBase`2.Get(TId id) in d:\Dev\Umbraco6\src\Umbraco.Core\Persistence\Repositories\RepositoryBase.cs:line 100
   at Umbraco.Core.Persistence.Repositories.MediaRepository.<PerformGetByQuery>d__b.MoveNext() in d:\Dev\Umbraco6\src\Umbraco.Core\Persistence\Repositories\MediaRepository.cs:line 102
   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at Umbraco.Core.Services.MediaService.RebuildXmlStructures(Int32[] contentTypeIds) in d:\Dev\Umbraco6\src\Umbraco.Core\Services\MediaService.cs:line 1002
   at Umbraco.Core.Events.TypedEventHandler`2.Invoke(TSender sender, TEventArgs e)
   at Umbraco.Core.Persistence.Migrations.MigrationRunner.Execute(Database database, DatabaseProviders databaseProvider, Boolean isUpgrade) in d:\Dev\Umbraco6\src\Umbraco.Core\Persistence\Migrations\MigrationRunner.cs:line 86
   at Umbraco.Core.DatabaseContext.UpgradeSchemaAndData() in d:\Dev\Umbraco6\src\Umbraco.Core\DatabaseContext.cs:line 544

I have the process bar stucked at 90% with no evolution and no error message.

Can anyone help? I am out of ideas 

Thanks in advanced.