I have a Windows 7 x64 desktop (computer name: MPC) and a Windows 7 x64 laptop (computer name: MLP). I have several folders I want to sync between the two. However, recently I found out that sync center wasn't opening or syncing (but it had always opened before). Upon further investigation, I realized that I could no longer access my desktop: MPC. If I clicked the computer in "Network", it would say "A device attached to the system is not functioning" along with a generic error message about authentication problems. After rebuilding the offline files cache with a registry edit ("FormatDatabase"), I could click on the MPC in Network with no problems. However, once I chose files to sync for "always available offline", I could no longer click on the PC inside "Network" without an error message. It happened immediately. All I had to do was start syncing and then I'd no longer have access to the network drive. The weird thing is if I clicked MPC in Network, I'd have the error message. But if I typed the IP address in the address bar like "\\192.168.1.xx", it'd work fine. Also, if I typed "\\MPC\Users", it'd also work. To find out whether the desktop or laptop was the one malfunctioning, I used a virtual machine to sync the same offline files from the desktop. It worked fine. For conclusive results, I also used the laptop to sync another network computer's (computer name: SA1) files. The same problem occurred again: once I pressed "always available offline", I would no longer be able to click on "SA1" in "Network" without an error. I tried connecting the laptop to a wired LAN and also using wireless. I cleared network authentication with "net use". I also completely reinstalled Windows 7 x64 on my laptop. The problem still exists. Can anyone help?

I have the exact same problem. It started only a little while ago. I'm guessing it happened with an update?

I'm guessing that if it happened with an update, many people would have noticed. What's your configuration like? Maybe there's something in common.

I'm experiencing the same problem - offline files sync stopped working a few days ago and now I can't map a network drive on my laptop (mapping a file from my desktop computer) and I'm getting the "A device attached to the system is not functioning" error message when I try opening the desktop from the list of network places on the laptop. Any good leads yet on a solution?

Hi, Please turn off Firewall and test it again under Safe Mode with Networking. If the issue still occurs, run SFC/scannow to verify the integrity of System Files. Juke Chou TechNet Community Support

Turning off firewall and testing under safe mode with networking yielded no results. There isn't an option for "Always available offline" in that mode. Using "sfc /scannow" under administrator command (on both server and client) returned no errors within system files. What should I do now?

SUCCESS, so far... I initiated a system restore back to a point immediately before the last major update "Microsoft .NET Framework 4 (KB2600217)" I immediately had access again to my offline files, Sync Center is working again, etc. Now, I'm not sure what to do about that .NET Framework 4 update if it comes up again my automatic system updates. Hope this works for you as well.

No, that does not fix the problem on my machine...

UPDATE: was working until I updated Avast Internet Security to v 7.0.1407 -- then lost all Sync Center and mapped drive networking capabilities. I've now completely uninstalled Avast (unfortunate - 'cause I've like that program for the last couple of years) and am back to being able to offline sync again. I looked into this a bit and came across the article below -- so, perhaps it wasn't the Microsoft .NET Framework updates afterall... http://forum.avast.com/index.php?topic=93995.msg748287#msg748287 Topic: Avast 7 kills Offline files synchronisation (Read 954 times)

Thanks a lot! Confirmed Avast 7 is the culprit. Time to submit a support ticket with Avast.