Clients timing out with no apparent reason I have a SQL Server 2005 server that's been running fine most of the time.

Today the users started to get time outs when opening new connections, including myself when I tried to open another tab on SSMS.

I've looked everywhere for the problem but I haven't found anything actually wrong with the server!

It's over 10.000 seconds of PLE, >99.80 cache hit ratio, Target Memory of 10GB and using only about 4GB. The server has 16 processor and the load is well below 20%. The I/O is pretty low, most activity comes from logging and CHECKPOINTs and only rarely the Lazywriter has to write stuff to disk.

This server is always been pretty underutilized, and still today I started getting timeouts when opening new connections.

The server has been restarted and the problem persists.

My first thought would be to blame the network, but I have remote DAC setup and I've been able to connect to the server without any delay when using the DAC, so I'm not so sure it's the network.

How can I track this problem down and diagnose what's going on? What tools or techniques can help me solve this?
Have you checked the error log? In Object Explorer, expand Management, expand SQL Server Logs, right-click Current... and choose Show SQL Server Log. Hopefully there will be more details there about what is causing the timeouts. If you can post anything suspect that you find there, we can help you troubleshoot further (though it may be something obvious, like a logon trigger or resource governor).