Well that usually means that there is already a file/node with the same name so you can't create a new one at the same place. Are you sure there isn't already a node with that name? Perhaps created by someone else?
Also it would be unusual to create a JSP under /content - normally all JSPs would be created under /apps/<myapp>/components/somecomponent/contentpage.jsp. Are you creating you JSP in the right place?
1. Did you earlier create and then delete some nodes under the folders you are working on?
2. Did you make too many changes without saving after each change?
3. Close the browser. open a new window. Clear the cache to be sure. Redo the changes (you could choose different node names) and save each time after every change. Doing this seems to solve the issue in most of the cases