If you need to go back to 4D Server v6.0.x after upgrading to v6.5 for whatever reason, here are some steps to keep in mind:
1. You will need to go back to a copy of the original v6.0.x version of your structure file.
2. The data file you are using with v6.5 is "backward compatible" and can still be used with your v6.0.x structure file. (ie: you won't lose your work!)
3. You will need to remove the .res and .rex files on the client machine. If you don't, you will probably get a message when connecting to the server that reads "Resource cache could not be created."