What computer operating system is your Premiere Elements 7 running on? What are its computer resources - installed and available RAM, free hard drive space, processor, etc?
What size project is this new project that you want to save? When you talk about "save", I am assuming that you mean saving the project prel file for further edits later. Is that correct? Or, are you talking about "save" in the sense of exporting your Timeline content to a file saved to the computer hard drive or to burn to disc?
Is this type of problem
a. It worked before but not now
b. It never worked before?
What is on that Timeline - video (format and duration), still (pixel dimensions and how many), and other?
Let us start here and then decide what next.