Update: This also appears to be happening on IE7 after the installation of recent Windows Update KB963027 - Thanks Virinder for the update.
The following errors appear in the Security Event logs:
An account failed to log on.
Subject:
Security ID: NULL SID
Account Name: -
Account Domain: -
Logon ID: 0x0
Logon Type: 3
Account For Which Logon Failed:
Security ID: NULL SID
Account Name: phil
Account Domain: PORTAL
Failure Information:
Failure Reason: An Error occured during Logon.
Status: 0xc000006d
Sub Status: 0x0
Process Information:
Caller Process ID: 0x0
Caller Process Name: -
Network Information:
Workstation Name: PACSERVER
Source Network Address: 192.168.105.1
Source Port: 57620
Detailed Authentication Information:
Logon Process:
Authentication Package: NTLM
Transited Services: -
Package Name (NTLM only): -
Key Length: 0
The sign in request seemed to be trying to log me on using a domain name called PORTAL, which doesn't exist but is the NetBIOS name of my SharePoint site URL - portal.pacdomain.local. When I tried signing on using the DOMAINNAME\Username format, the logon failed with the same message in the event logs.
To resolve the issue, I followed the steps documented in the following article - http://support.microsoft.com/kb/956158/en-us, which seems completely unrelated to the issue I was having as it references a problem when using SQL Server 2008 Reporting Services.
Update: This issue is also discussed in the following Microsoft article - http://support.microsoft.com/default.aspx?scid=kb;en-us;896861