We too have the following error on our win 2k3 X64 cluster system using SQL2005 . Here is the cluster log leading to cluster failure as pointed out by earlier posters on this thread .

000008d0.00000610::2008/06/19-08:56:49.653 ERR SQL Server : [sqsrvres] CheckQueryProcessorAlive: sqlexecdirect failed

We plan to change following para in registry and eliminate the write cache on storage .

HKLM-->System-->CurrentControlSet-->Services--TCPIP-->Parameters

Change the following entries to 0 and reboot

EnableTCPChimney

EnableTCPA

EnableRSS

Will this solve the problem.

We have also increased the isalive and lookslive values from 5000 and 60000 to 6500 and 80000.

Does this looks ok .

We use VNC , at time RDP and performance logs monitoring . Further SQL memory is et to utilize max physical memory (physical memory - 8GB) .