Friday, January 18, 2008

Vista hangs at login with "Windows is waiting for the user profile service"

Along with a change to TCP offloading on our server, a staff member on a Vista machine started encountering a problem when logging in; her computer would hang with "Windows is waiting for the user profile service" on the screen.  Checking the service status from a remote computer showed this service as "Starting..."

Although I really wanted to remotely debug this issue (grab a stack trace with a debugger attached), the user was anxious to get back to work which means I had to work quickly.

I stumbled upon a feature named TCP auto-tuning or TCP window scaling.  It turns out, this feature also ties into TCP offloading, which we just disabled on our server due to a Broadcom issue

You can turn off auto tuning from the command prompt by running

netsh interface tcp set global autotuninglevel=disable

Sure enough, after running this (from safe mode), the user was able to login again.

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