We're aware of a Sophos bug that causes Microsoft Internet Explorer 8 to freeze upon start up or while opening a new tab. This bug can be exacerbated when Google Toolbar is installed.
This problem appears to be related to a component of Sophos's buffer overflow protection.
please visit this Sophos Support Community thread for details of the problem and a few recommended workarounds.
We will keep you posted as we work with Sophos to resolve this issue.
Google Toolbar Help: Conflict with Sophos Endpoint Security Software