add sitemap gives error and deletes existing sitemap

I just installed the latest dev on my local testsite. (wamp server)
When I add another sitemap I get the following error:
recoverable fatal error: Argument 1 passed to xmlsitemap_sitemap_save() must be an instance of stdClass, array given, called in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.admin.inc on line 238 and defined in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 381.
recoverable fatal error: Argument 1 passed to xmlsitemap_sitemap_get_context_hash() must be an array, null given, called in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 386 and defined in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 472.
warning: asort() expects parameter 1 to be array, null given in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 473.
warning: Attempt to assign property of non-object in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 386.
warning: array_fill() [function.array-fill]: Number of elements must be positive in C:\wamp\www\drupal\includes\database.inc on line 253.
warning: implode() [function.implode]: Invalid arguments passed in C:\wamp\www\drupal\includes\database.inc on line 253.
user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1 query: SELECT * FROM xmlsitemap_sitemap WHERE smid IN () in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.module on line 343.

Also the default sitemap (the one that is automatically created after installing the module) is deleted.
Now there are no XML sitemaps available.
Then I click "Add new XML sitemap".
Then I choose the desired language. (I have a multilingual site)
I choose English.

Then I get the following error:
Fatal error: Cannot use object of type stdClass as array in C:\wamp\www\drupal\sites\all\modules\xmlsitemap\xmlsitemap.admin.inc on line 232

I enabled following XML sitemap modules:
XML sitemap
XML sitemap internationalization
XML sitemap node

I uninstalled and reinstalled the module(s). Still the same issue.