NTLM SSO+IE 6-8+Downloader+Connection Error:Server Error:500

I’m using Vaadin 6.8.3 version and implementer Kerberos/NTLM solution using spring-security (with spring version 3), using SPNEGO and NTLM filters.
Uploading file(special signatures), that gets validated and report from the validation (of certificates, signatures and others) downloaded after the validation using
The application has 3 modes (without SSO, NTLM and Kerberos)

In Firefox i’m not getting this error, it happens only in IE and only for the settings with NTLM

To upload files that gets validated i’m using normal Upload component, but triggered manually with submit upload(with progress), after preliminary validation of the form with upload is performed when the upload started (received upload) and (uloadFinished) (upload, backend gets called and perfoms all the validations) and automatically different file gets downloaded with results of the validation

Sometimes in IE for the setting NTLM im getting the error, Communcation problems: Server Error: 500, despite of the fact, that the result gets downloaded and verifycation data gets displayed in the form.

i looked in the debug console in vaadin debug mode and can se that the error is caused one of the requests comming from vaadin.(request without parameters on UIDL)

Without autentication it works correctly, with kerberos also, but ntlm IE 6-8 is sometimes showing this error, i suppose this has nothing to do with authentization type.
ntlm authentication finishes without errors, but with the upload component.