Starting yesterday, we started noticing problems with some menus in LabKey Server with the latest update to Chrome, version 43. We're hopeful that a future Chrome update might resolve the issue, but are working on a patch to avoid the problem:

https://www.labkey.org/issues/home/Developer/issues/details.view?issueId=23352

In the meantime, earlier versions of Chrome and all other browsers don't exhibit the problem.

Thanks,
Josh

Update: Sencha is aware of the issue and is working on a fix themselves, but encourages developers to work together to find workarounds as well.

https://www.sencha.com/forum/showthread.php?301116-Submenus-disappear-in-Chrome-43-beta&p=1100997