I tried that MANY times! I uninstalled & re-installed 3 times! The problem is on YOUR end! A patch needs to be developed, quickly! I can't work if I can't edit mp3 files!
Please remember these are user to user forums, so your problem is not OURS and we can do nothing about it! If you wish to create a Support Ticket please start here, making sure you fill in ALL the details requested on each page and always clicking on the "Ask Support" option of each page.
Make sure you are reinstalling the latest SF build. The problem is common and has been allegedly fixed in the latest build. You can try uninstalling using a third-party app that can also remove left-over registry entries and other pertinent data the OS uninstall leaves behind, which in usually the root of recurring issues . Revo Uninstall has pro and freeware versions, the free version is usually adequate in most cases. Then reinstall Sound Forge.
A work-a-round is saving the file as a PCM <.wav> file and use an standalone MP3 encoder. I like the WinLAME RC3 (GUI) LAME encoder which has more parameters than most. It can also batch convert