Install problems on existing site

Hi,
I have a tried to install Open Enterprise on an exiting updated Drupal 7.17 site. The content is placed in sites/all/modules folder.
After install I go to "modules" to enable apps, but when I save this configuration the whole site crashes and I'm left with this error:
Fatal error: Cannot redeclare field_info_cache_clear() (previously declared in /home/skakikol/sites/test1/modules/field/field.info.inc:29) in /home/skakikol/sites/test1/sites/all/modules/openenterprise-7.x-1.0-rc3/modules/field/field.info.inc on line 38
I can't even re-install the module, so the site must be restored.
Somehow I'm doing something wrong here...
Can anyone help?