Windows 7 64-bit freeze/deadlock condition

Hi all,

Since our migration to Windows 7 64-bit we have been experiencing intermittent 'freezing' issues.

This is generally when a user connects to our VPN using the Cisco Anyconnect VPN client, however this issue has also risen when a machine has been moved from one network to another. i.e. unplugged from private network then plugged into our corporate network. This issue is very intermittent and only affects approximately 25% of our machines. These affected machines may only exhibit this symptom once a month, or multiple times in a row.

The symptom is:

•     User connects to VPN
•     After an unspecified period of time (1 second to 10 minutes)
•     Cannot open new applications. the process appears in Task Manager, but the program never appears on the screen. The cursor will change to the spinning icon for a few seconds though.
•     Already open applications appear to function normally.
•     Mouse and keyboard function normally
•     Cannot disconnect from VPN or shutdown computer
•     System 'unfreezes' if the user kills the svchost.exe -netsvcs process in Task Manager. (The trick being that the user must have Task Manager open before the system freezes, else they cannot open Task Manager to kill svchost)

I have contacted Sophos support regarding this issue, but the case was closed with no resolution. Due to the intermittent nature of this issue and the non-technical nature of the staff having this issue, I was not able to provide procmon logs within the case timeframe.

I have tested:

• Disabling the firewall
• Disabling on-access scanning
• Disabling BOPS
• Sophos version 9.x and 10.0
• Latest version of Cisco Anyconnect client
• Fully patched version of Windows 7 SP1 64-bit enterprise

Has anyone had any similar issues, or idea's with regard to troubleshooting?

Thanks in advance,

Jake.