Hello Scott
Did you uninstall Firefox 1.5 and its install folder before loading Mozilla 1.7, as there are known problems if you install over the top. http://www.mozilla.org/docs/end-user/guide/get-started.html#before-installing-mozilla Follow the instructions to the letter, or problems will occur.
My personal recommendation is to uninstall Mozilla 1.7 and reinstall Firefox 1.5, unless you really need the extra features of Mozilla 1.7.
Hope this helps.

Bill