Same – maybe worse – problem here. After upgrading (I tried with a fresh installation as well) on local host, WordPress (both site and admin panel) just hangs till it stops loading, showing a blank page. It loads correctly (but very slowly) once every 100 or so retries. Also, I noticed that Apache started randomly crashing when loading WP2.7. I’m on Windows XP, and all other sites (including old WP versions) on my pc work well as always.