In the last few days I was developing a SharePoint 2010 solution, including a feature with a custom action.
In the middle of the testing / fine tuning process I suddenly realized that my custom action does not work anymore. When I clicked on the menu simple nothing happened.
Restarting the browser (Internet Explorer 8 in my case) or clearing IE cache to remove potentially corrupted cached .js files does not help nor does the “standard” IISRESET and server restart to exclude server side issues.
However, built-in menus in the edit control block (ECB), Site Actions and Welcome Menu also suffered from the same problem.
To decide whether it is a client or server side issue, I visited another server from my machine. This server runs MOSS 2007 but I found the same problem with the menu when visiting from my developer server.
It gave me some hope and help that when started my browser InPrivate or started its x64 version the sites showed their normal behavior.
I found that disabling the add-ons solved the issue, so the next step was to locate the add-on that was responsible for the behavior. I disabled the add-ons one by one in the Tools / Manage Add-ons menu in IE 8.
In my case a DivX add-on was accountable for the issue. A few days ago I installed a DivX codec that included add-ons as well, but the behavior started only yesterday, probably when I restart IE the first time after the codec installation.