Ha... It are the things like these that keep maintaining CCMS a unique experience

. I've seen the error on your site (u is undefine (Javascript error)). I was able to reproduce this error by removing the following line from ./admin/editor.php
<script type="text/javascript" src="includes/tiny_mce/plugins/tinybrowser/tb_tinymce.js.php"></script>
So something appears to go wrong with including this file (which defines the necessary u). It goes without saying that it seems very strange that one server has trouble with this and another has not.
1) First thing I'm going to ask you is to open ./admin/includes/tiny_mce/plugins/tinybrowser/config_tinybrowser.php
2) Then find the line saying
set_time_limit(240); and disable it. E.g. replace it with
//set_time_limit(240);3) Save, upload and check again.
If this doesn't work, try replacing the include line mentioned in the code box above to directly under this line: <script type="text/javascript" src="includes/tiny_mce/tiny_mce_gzip.js"></script>
Let me know whether this changes things, and if not: keep the changes online so we can see how it has affected error reporting.
Cheers,
Xander.