If you are getting Timeout or Pre-login Errors when trying to access MS SQL Server Express 2008 from a Windows Vista based client then read on!
Some of the reasons behind these errors (and the solutions) are given here:
http://technet.microsoft.com/en-us/library/ms190181.aspx
If the above does NOT resolve the error (as in my case) then before you start cursing Microsoft try this:
Go to the Network and Internet –> Network Connections
Right click on the connection being used (WiFi or LAN or any other).
I found IPv6 and and Link-Layer Topology protocols enabled which I disabled.
This partially resolved the issues. Database access was quite stable and I was able to do some of the work. But still things were not 100% normal. I was loosing the wireless connection and it was showing me connected to an ‘unidentified network’. Even the internet stopped working if the computer went into standby.
This it seems is a very common problem and more info can be found on the Microsoft site.
This problem results from
A) Issues with DHCP implementation difference between Vista and XP.
Read for solution: http://support.microsoft.com/kb/928233
B) Issues with power management profiles and WiFi networks
Read for solution: http://support.microsoft.com/kb/928152