File manager uploads disappearing ?

I am having an odd issue with file manager uploads, using any of the file manager, media browser or file upload dialogues in the modx manager I get the same issue. I can pick a file, click "upload" and it will give me an "upload successful" message. But the file does not actually get saved to disk!!

I've checked the directory it was supposed to be uploaded manually, it's not there, nor in the root of the site.

- I can create directories using the modx manager, but just not upload files into it.
- no errors in the modx logs
- no errors in the apache logs
- all the php settings and file max size restrictions check out
- allowed file types also all check out.

A little bit baffled here - has anyone come across (and solved) an issue like this?

-thanks
-sean