Hi I have had this problem with Service Desk plus where it will work for around a day or two but then it will halt and appear that it is still working, but new requests which are emailed in arn't picked up and created as new jobs.
I will then have to stop the Service Desk service and start it again and then all the emails that have been sent throught the period of when SD has stopped working will all be created as new jobs as soon as the service is back up.
This may have started happening when we moved the database on the MSSQL 2000 from one partition to another when we were running build 7000. I have recently updated it to build 7514 but still am expereincing these issues. Occasionally I have noticed that the Java.exe process is using around 80 - 90 % of CPU usage when SD crashes.