You should always make sure the version of the Developer’s tools match the version of the product that you’re working with. You can download the latest tools from a running 6.6x Rhythmyx server by using the URL below:
That being said, if you weren’t previously having problems with the 6.5x WB and now other users also encounter this same behavior on different machines, the problem may be something with the server itself. I recommend trying to install and use the latest Developer tools. If you still have trouble, submit a new ticket with Tech Support.