Add existing Module worked as expected.  Have you a custom Skin ?  If yes try to use hosted jQuery and jQueryUI to older Versions of it.  If you have some JavaScript in your Skin or module that uses older jQuery versions it could brake the other scripts. 

Also you have first select a page in the add existing Module fetaure before you can add a existing module.

Hi Hossein,

it looks as the module is not automaticly added to the allowed module.  Please go to your module in the extensions and click edit Extension. Then set 'Module Category' to 'Common'.  Most of modules missing this Attribut in the manifestfile, so it is not set and not listed as availible module.