microtime is not enough :)
This errors happens because of a unique-ID-generating-function uses microtime. On some machines the microtime-based function does not provide unique IDs.
Under certain conditions, when using TMENU_LAYERS the layers containing the navigation items get non-unique IDs.
We noticed this error after migrating several sites in a virtualized environment on a very fast machine.
To correct this error we used the php-function uniqid to give us unique ids.
We proceeded this way:
- locate the file /typo3/sysext/cms/tslib/media/scripts/tmenu_layers.php
- search for the string: substr(md5(microtime()),0,6);
- replace the string using: str_replace(‘.’,‘’,uniqid(‘’,true));
We also filed a bug