I was experiencing the same issue. It just started today. I looked at the Firebug console and it said there was an issue with the parent document's pagetitle when being parsed by ext-all.js (line 21, col 60):
SyntaxError: missing } after property list
error source line:
...parent-cmb":"Product User Guide (" Hot Chocolate" Edition) (485)","syncsite...
I find this interesting, because The actual pagetitle of the document is:
Product User Guide ("Hot Chocolate" Edition)
Notice that my pagetitle uses "amp;. It does not use plain quotation marks. Somewhere along the line, MODx is converting my HTML entity into plain quotation marks, and this is breaking the code. So I removed both instances of " from my pagetitle, and now when I save one of the child documents, the save works properly. This is reproduceable. I put " in, and I get the error when saving a child document. I take " out, and the error goes away.
Just out of curiosity, I tried saving it with plain quotation marks, and there is no error.
This seems like a bug that can probably be remedied pretty easily in the MODx source code by anyone who wants to take that on.
(By the way, I had a hard time forcing this discussion forum to write ". I had to cheat and write ". Otherwise this forum converts it automatically to a regular quotation mark.)
[ed. note: paulbohman last edited this post 12 years, 9 months ago.]