Answering in reverse order:
Another problem is with my admin bar. Admin bar has it’s menu broken. The number in the update notifications and the new in the add new and page in the edit page options are pushed to second row. Not even deactivating all plugin’s and reinstalling wordpress is helping.
This is not caused by ai1ec – it sounds like your database might be corrupted?
The problem arises only when the version is upgraded to premium. I uninstalled the plugin but the theme doesnt uninstall and i had to manually delete ai1ec theme folder.
When you uninstall the plugin, events are deleted. Themes on the other hand are not deleted because there could be custom work you have done on them. We don’t want to delete something that you have created. So theme folder is kept but it doesn’t cause any problems to the wordpress install. There is only one positive side, if you ever decide to use the plugin again and you created a custom theme, it will be available when you install the plugin. Uninstalling the plugin deletes all events data and categories and tags etc – It is explained during the uninstall process.