Migrating 3.7sp4 to 6.1 - template error - UnauthorizedAcces

I am trying to migrate a site from 3.7sp4 to 6.1.  I am getting an error when it tries to migrate the templates. 

This is the message in the log:
""Registering template "Base"...
""Error occurred during the migration of template Base.

And this is the detailed message:
Timestamp: 10/14/2013 4:58:08 AMMessage: Registering template "Base"...
----------------------------------------
----------------------------------------
Timestamp: 10/14/2013 4:59:01 AMMessage: HandlingInstanceID: 9e6ad28c-d529-4502-b2fa-87b3260660d9
An exception of type 'System.UnauthorizedAccessException' occurred and was caught.
----------------------------------------------------------------------------------
10/14/2013 00:59:01
Type : System.UnauthorizedAccessException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
Message : Access to the path 'C:\Program Files (x86)\Telerik\Sitefinity 6.1\Projects\test1\App_Master\Base.master' is denied.
Source : mscorlib
Help link :
Data : System.Collections.ListDictionaryInternal
TargetSite : Void WinIOError(Int32, System.String)
HResult : -2147024891
Stack Trace :    at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize, Boolean checkHost)
   at System.IO.File.InternalWriteAllText(String path, String contents, Encoding encoding, Boolean checkHost)
   at Telerik.Sitefinity.Modules.Migration.Actions.ContentParser.ProcessMasterPage(MigrationMasterPage masterPage)
   at Telerik.Sitefinity.Modules.Migration.Actions.ContentParser.ProcessMasterHierarchy(List`1 masterHierarchy)
   at Telerik.Sitefinity.Modules.Migration.Strategies.Templates.Operations.TemplateCreateMasterPagesOperation.Process(OperationContext context)
   at Telerik.Sitefinity.Modules.Migration.MigrationOperation.ExecuteOperation(OperationContext context)
   at Telerik.Sitefinity.Modules.Migration.Strategies.Templates.Operations.TemplatesCreateOperation.Process(OperationContext context)

And just for the hell of it since i was getting UnauthorizedAccessException, i gave Everyone full control of the App_Master folder, but i still get this same error.

Hi Jason,

It seems that the App_Data folder does not have write permissions and this causing the problem.

Message : Access to the path 'C:\Program Files (x86)\Telerik\Sitefinity 6.1\Projects\test1\App_Master\Base.master' is denied.

It is good tho know that during the migration progress both the projects should be deployed on IIS. You can find detailed information about the migration process in the following article from our documentation:

Migrating your Sitefinity 3.7 project

Regards,
Kaloyan
Telerik