Currently, I am running Redhat 5.2 and the Sybase database server. For some unknown reason, after a large number of transactions, the Sybase dataserver process goes into a "D" state (uninterruptible sleep). Also, some other Sybase sysmultibuf processes remain. I have not been able to determine why the dataserver goes into the "D" state. It is suspected that there is either s software bug in the Sybase server or the kernel. Once the process goes into the "D" state, the file system capabilities are limited. I can still access files and do maintenance, however it prevents admin functions like umount and sync from being executed. If these are run, they will go into a uninterruptible sleep also. These problems make a software reboot of the system impossible, because the processes will never shutdown. A hard boot is the only method of cleaning the state.
Do not have the resources to replicate this in test lab. Verify that you are running the latest version of the 2.1 kernel. as this might have an effect on the way that things are interacting.