When the logged on user initiates a synchronization through the sync center we see an error in the sync center that the IE index.dat file is in use and cannot be synchronized. And you wont see this error when the sync is forced during reconnection or log-off.
This Happens, When you have roaming profiles and folder redirection ( desktop, appdata, favorites, Pictures, Videos, Docs, desktop ).
It seems the IE index.dat file causes the problems. You can try to delete some index.dat files if you want to.
Solution:
Whether for better administrative control, security or as a means to keep the client workstations lighter and more energy efficient, application data is being redirected to remote disks increasing the amount of user data to be stored in a central location.
However, Internet Explorer performance and stability can be impacted greatly from such a configuration. Internet Explorer utilizes a number of caches for user browsing data. The most common of these are the Temporary Internet Files, History and Cookies folders.
Each contains a reference database, index.dat, which allows Internet Explorer to keep track of the location of individual pieces of browsing data and other relative attributes of that data, such as expiration and last-accessed dates. It should be fairly evident that these indices are constantly being read from and written to during the course of a browsing session. Each object being requested has to be looked up to determine if it exists and if so, its attributes have to be enumerated. If not, the client must download a copy of the object, place it into the appropriate cache and then update the index with its location and applicable attributes.
Consequently, the resulting behavior that is displayed to the user can vary from Internet Explorer becoming unresponsive to missing or poor content layout.
The question then becomes, what are Microsoft’s official recommendations?
Simply put: Do not redirect the user’s Internet Explorer’s folders. Internet Explorer currently does not have the capacity to reliably utilize its data files from a remote location. Outward signs (error dialogs, event logs, browser behavior) do not indicate that the problem is caused by inaccessible indices. The sooner those administrators revert from this practice, the less impact there will be when organizations grow.
Eventually, once discovered, the issue is resolved with the recommendation to return the folders to their proper locations on the local machine.
If your organization is focused on maintaining site preference cookies for users with roaming profiles, it may be easier to leave the user shell folder locations set at their recommended default values and then incorporate a policy to force the clients to empty the Temporary Internet Files when the browser is closed. This will result in a small cache to copy across the network when the user logs in or out. The cookies should be preserved and roam as expected.
Simple recommendation would be, do not redirect "appdata". And if you already have redirected these folders, start building a contingency plan and detail the time and resources required to undo it.
Also, using group policy preferences you can redirect the following reg keys to the local appdata. This will solve the the problem.
Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\Cookies -> To %USERPROFILE%\AppData\Local\Microsoft\Windows\Cookies
Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\Cache\Extensible Cache\ietld\CachePath -> To %LOCALAPPDATA%\Microsoft\Windows\IETldCache
Software\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\LowCache\Extensible Cache\ietld\CachePath -> To %LOCALAPPDATA%\Microsoft\Windows\IETldCache\Low
