unable to install

Somethin bizarre happened. I uninstalled Webform module via uninstall tab in Modules. Then I installed latest version via FTP (I know how to do it as I am using Drupal for 5 years). now Webform does't even show up in Modules list. any idea?

I tried to install with Drush and got following warnings:
WD php: Warning: array_keys() expects parameter 1 to be array, null [warning]
given in gardens_features_system_modules_submit() (line 470 of
/home/acamedium/public_html/sites/all/modules/gardens_features/gardens_features.module).
WD php: Warning: Invalid argument supplied for foreach() in [warning]
gardens_features_system_modules_submit() (line 470 of
/home/acamedium/public_html/sites/all/modules/gardens_features/gardens_features.module).
WD php: Warning: array_keys() expects parameter 1 to be array, null [warning]
given in gardens_features_system_modules_submit() (line 470 of
/home/acamedium/public_html/sites/all/modules/gardens_features/gardens_features.module).
WD php: Warning: Invalid argument supplied for foreach() in [warning]
gardens_features_system_modules_submit() (line 470 of
/home/acamedium/public_html/sites/all/modules/gardens_features/gardens_features.module).

PS: my drupal site is exported from Drupal Gardens and updated several times