In CS4, I had the same message and fixed it by changing the location of the scratch disks back to under the Adobe Premiere Pro folder. Once I did that, it rendered fine. I also am on a network. I had the same problem in Captivate and wonder now if this will solve that problem as well. Bottom line is, when you first set up a new project, do not create / save scratch disk folders outside of the c:/program files/Adobe Premiere Pro CS4 folder.
I didn't find this solution anywhere, so please copy and paste if you're logged in elsewhere and it works for you. THX.
JS
