W2K8R2 logon fails but eventually succeeds

[disturbedone]

We've had it reported from a few users that when the logon from XPSP3 clients to our, newly upgraded from W2K3R2 (1mth), W2K8R2 domain that it says they cannot be logged on. I'm unsure of the exact error because I haven't seen it myself yet. But after several (2-3) attempts it will log them on. They assure me that they are entering their credentials correctly.

A couple of things to note, although I'm not sure if they're related or not.....
1. These student machines use Faronics Deep Freeze
2. We use Netbox Blue proxy/filter and there have been issues (slowness) with it authenticating users to allow them Internet access. Not sure if this is an issue with the Netbox software of not. A reboot of Netbox resolves it (temporarily, eg 2-4hrs) and since a reboot of the 2 DCs it hasn't needed a reboot in 8hrs.

Is there an issue with W2K8R2 authentication going slowly?

 

[joepc]

Only if your internal DNS is wrong or if you have trouble connecting to a DC.

 

[disturbedone]

Lots of Googling found this

http://support.microsoft.com/kb/975363

The title is a little misleading as the user isn't prompted but does receive extremely slow Internet via the proxy server.

If the server is busy with NTLM requests then is this also causing the issues with logon???