"login failed for user '(null)'" 1

[squiddy]

SQL Server 2k on Win2k Server
NT Domain Controller
Win2k client machines.

For the last two months, SQL has worked just fine. Now, suddenly, Client machines can no longer connect to the server using Windows authentication. They can, however, connect using SQL authentication. No changes made in last week to clients or server. We're fully licensed, that shouldn't be an issue.

Any ideas? Any other info you need?

 

[foxdev]

I've had this experience on occasion, and I recall another thread here about a month ago of someone who could not authenticate from a particular machine. In both cases, either restarting SQL Server service or rebooting the BDC solved the problem; root cause was never determined. Robert Bradley

http://www.agrainofhope.org

http://www.lowcostprints.com

http://www.foxdev.com

 

[Hal10K]

Hmmm,
Haven't had the problem much since SQL 6.5, but it can happen in 7 and 2000. Check your server activity. If you see blocked spid, you have users contending for the same resource. This might be a reason.
Check for orphaned connections. This most often happens when users reboot their machines because they are "locked up". Get enough orphans and the server, (especially prior to 7) just flat won't do anything, and will have to be restarted. The cure for orphans is defensive coding at the client end, (time that connection out), user education and Memory.....
Our problem a coupla years ago went away when we gave the server and the clients lots of RAM....

-hal

 

[aalmeida]

I had that problem with SQL 2k on win2k, but it was the beta version on the LAB, I was never able to properly identify what caused it, rebooting the PDC it would help and it would work again for some time and them again no win Authentication.
With the real thing and it has occurred before the SP1 for win2k and SQL server 2k after SP1 installed it has never occurred so far.
I'm not sure if there is a fix on the service packs but it seems to me a good place to start, what is the SP level on all servers?
AL Almeida
NT/DB Admin
"May all those that come behind us, find us faithfull"