I have noticed a similar question to this having carried out a search but the answers given are unfortunately not helpful in my situation.
I am currently carrying out Windows 7 deployment and a handful of pilot users have mentioned that when taking their machine out of sleep mode they are asked for their Outlook credentials before being able to reconnect to the Exchange server. I believed that the issue was related to the option to allow the NIC power down when in sleep mode in order to conserve power - however having made the relevant changes within the build process I have noticed that the problem persists. Another reason why I am certain it does not relate to the NIC card powering down is that all other network connectivitiy functions correctly when removing the machine from sleep mode.
Has anyone come across this issue before? Any help on this would be greatly appreciated as I envisage the service desk being inundated with end user queries as to whether the network is down due to Outlook requesting credentials.