After the automatic update to 3.5, I'm another who is having this problem. All I can see is the text editor - the tab for visual editor is there, but does nothing.
After reading other threads on this topic, as is suggested, I have been very sensible and done the following:
1. Deactivated all plugins, etc, one at a time in both my usual theme (Comet) and Twenty Eleven.
2. Switched to the Twenty Eleven theme, to check Comet.
3. Cleared browser's cookies and cache (Firefox, but this isn't working in IE either).
4. Logged out and logged in.
5. Created a new post to test.
6. Ensured all plug-ins are updated.
7. Checked the WP 3.5 troubleshooting page (but this isn't mentioned, which is surprising?)
8. User profile - Disable the visual editor when writing box is unchecked
9. WP 3.5 reinstalled from dashboard
Nothing has changed. I'm not a designer or developer, so don't want to go into the engine room with a spanner... unless I have very good, idiot-proof instructions. What next?