Problem Summary. When using custom menus in WordPress, and adding too many menu and sub menu options, it’s possible that when saving/updating the menu customizations and changes that you will get an error message stating, “Maximum execution time of 30 seconds exceeded…” and some information about where that error occurred.
Problem Solution. To fix this problem, edit the wpconfig.php file as indicated below.
Before editing, find the line in your wpconfig.php file that states:
/* That's all, stop editing! Happy blogging. */
Then, after that line, have a blank line and then add the following:
/* To eliminate time limit. */ set_time_limit(0);
This should fix the problem.