Apple released iMac Software Update 1.3 on Thursday evening. The scant update details say it provides fixes for important issues. It is intended for 20.GHz, 2.4GHz, and 2.8GHz 20 and 24-inch glossy display iMacs and requires Mac OS X 10.5. The 21.6MB download is available via the Software Update application, or as a downloadable installer at the Apple Support Web site.