SSPI handshake failed with error code 0x8009030c while establishing a connection with integrated security; the connection has be

Question

Hello, I have a sql 2005 server, and I am a developer, with the database on my own machine.  It alwayws works for me but after some minutes the other developer cant work in the application
He got this error
Login failed for user ''. The user is not associated with a trusted SQL Server connection. [CLIENT: 192.168.1.140]
and When I see the log event after that error, it comes with another error.
SSPI handshake failed with error code 0x8009030c while establishing a connection with integrated security; the connection has been closed. [CLIENT: 192.168.1.140]
He has IIS5 and me too.
I created a user on the domain called ASPSYS with password, then in the IIS on anonymous authentication I put that user with that password, and it works, on both machines.
and in the connection string I have.
<add key="sqlconn" value="Data Source=ESTACION15;Initial Catalog=GescomDefinitiva;Integrated Security=SSPI; Trusted_Connection=true"/>
I go to the profiler, and I see that when he browses a page, the database is accesed with user ASPSYS, but when I browse a page, the database is accesed with user SE\levalencia.
Thats strange.
The only way that the other developer can work again on the project is to restart the whole machine. He has windows xp profession, I have windows 2000.
If you want me to send logs please tellme

Answer 1

Well here's my problem, maybe you can help. Intermittenly I get a login failed when connecting to a db engine through Server Management Studio using Windows authentication. When this happens the following entries are generated on the server's application event log:
Event Type:        Error
Event Source:    MSSQLSERVER
Event Category:                (4)
Event ID:              17806
Date:                     1/14/2009
Time:                     10:41:31 AM
User:                     N/A
Computer:          <server name>
Description:
SSPI handshake failed with error code 0x8009030c while establishing a connection with integrated security; the connection has been closed. [CLIENT: <ip address>]
Event Type:        Failure Audit
Event Source:    MSSQLSERVER
Event Category:                (4)
Event ID:              18452
Date:                     1/14/2009
Time:                     10:41:31 AM
User:                     N/A
Computer:          <server name>
Description:
Login failed for user ''. The user is not associated with a trusted SQL Server connection. [CLIENT: <ip address>]
I've already ensured that the server is set to mixed authentication mode. Oddly enough, the workaround that I've found is that if I remote desktop into the server, log in and then log back out, Management Studio is suddenly able to connect again. No idea why it works. 
As I said before, it is intermitten. Some days it errors on login, other days it doesn't and there are no configuration changes between them. Also, both client and server are in the same domain and same site so there is no VPN or anything in between. I'm really quite stumped. Any help would be great, or if you can point me in the right direction of where to look. Thank you in advance!