After adding the DOM, swfupload and image_gallery modules into a fresh SS 2.4.0 install i started getting '$ is not a function' javascript errors.
As a result I'm unable to use the SimpleHTMLEditorField in a popup.

Any ideas what could be causing this?
I can't disable DOM as i need a WYSIWYG in a popup and drag & drop re-ordering.

I don't have access to that code right now, so i'll have to look into that tonight.
Best guess though: it happens even without SimpleHTMLEditorField.
Errors are not limited to the SimpleHTMLEditorField, but they also popup in other JS files.

My reason for pointing out SimpleHTMLEditorField is that because of the errors the fields don't work.
Rest of the application seems to work fine, with and without the error.

If i remember correctly the errors did disappear when i disabled DOM and IG and removed any DOM fields in custom code.
This i will also double check tonight.

As far as any other javascript, I don't have any other modules installed or any custom code using JS.

p.s.
I'm using the latest trunk versions of the modules.

Just did some testing.
The error appears whenever i try to edit a DataObject using DOM.
I think it's due to the fact that you clear all requirements and add the JS in your own way.

DataObjectManager.php line 752, class DataObjectManager_Popup
You add jQuery and prototype in there, which i suspect is causing the problem.
I tried adding a file containing jQuery.noConflict(); after the main jQuery file, but i still got the error.

I can't replicate the error on your demo site either (although I'm on a different computer at the moment).
Also my setup differs a bit from yours.

CustomPage
-- CustDataObject (managed by DOM, should contain 2 WYSIWYG editors)
---- CustFileDataObject (managed by FDOM, seperate tab in the CustDataObject form)

Also which versions are you using?
I'll try to setup an online demo tonight if the issue still hasn't been resolved.