Hi Venkat,
have you tried using an unmodified version of this plugin to test it’s not any changes you have been making to it that has caused these issues?
I would try that first.
The plugin also has a dedicated support forum and it might be good to ask this question there too http://wordpress.org/support/plugin/dropdown-menus
Hi Stuart,
Yes, I have tried un-modified version on plugin, before editing it. There were no issues.
But we started to face this problem (menus taking time to load and save) only after we were forced to change the max_input_vars variable to more than 3000 in php.ini to support longer menu items.