Using Drupal 7.15. When I enable Clientside Validation, AJAX file uploads stop working, and return this error in a native browser alert: http://pastebin.com/tfEqHkTn (example when trying to "Delete" a previously uploaded image from a node).
It happens just after adding base Clientside Validation module component, without any of ther others components active. When I disable the module everything works fine. Error appears both in admin area and public forms that allow file uploads. Also happens both in testing (2) and production servers.
I'm using the AJAX component for other things (i.e: calendar month navigation) and it works flawlessly so I don't think it's an AJAX-related problem. File uploads work when AJAX is not used, sending the whole form instead of field-specific upload buttons.
Sadly I currently don't have the time to look at code and fix, but i'll be monitoring here if more information is needed. Sorry about that.