Possibly the page isn't being transferred completely. If you view the page's source does it end with the expected </body> and </html>?
If you check your browser's console (for example: Web Console in Firefox) are any errors shown? How about when you click your name or Add an activity or resource?
If you check your browser's network monitor (for example: in Firefox) does it show any resources failing to load? If so, with what status and can you see any message from the web server in the response.
Also, try enabling debugging in config.php and see if anything appears in your error log that might help.