Warning: Variable passed to each() is not an array or object in me_handler() AND Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'css' not found or invalid function name in me_handler()

The same error makes WSOD sometimes, look at this other issue, looks similar to me:
https://www.drupal.org/node/2076691

Ran into a similar issue, triggering a WSOD on user_relationships links. Applied patch fixed it for me, but is not properly tested yet. I's strange that variables $parts and $callback are always set in me_handler if they are provided as function arguments?

Please try the 7.x-1.x-dev release and post here if you have the same problem

I was getting the first Warning listed above and then getting the WSOD mentioned here #2076691: Arguments passed to me_handler() in the wrong order. The 7.x-1.x-dev release fixed both.

I tried 7.x-1.2+3-dev, fixes this and other issues. thanx!

Just to reiterate, you will have a bad time if you just apply the patch in comment #3 above, if you have any paths with multiple load parameters. For example, consider the following:

/user/me/customobjects/123

Where you have a menu handler path definition like this:

/user/%user/customobjects/%customobject

The %customobject id will get passed as the callback, and you will get a whitescreen because it is not callable.

The fix in the dev branch is the correct fix, and does not result in this fatal error, nor does it register warnings in dblog. Can we get a stable release with this fix?

This was fixed in the 7.x-1.2 release.