Thanks Kyle for answering that fast. I've got it!
For the record:
If somebody is trying to uninstall UddeIM from the system Remember to uninstall the plugins from "community builder, first" before uninstalling the component from Joomla ---> Extensions ---> Manage
I've got into trouble, when unistalling UddeIM from the system. After uninstalling uddeim from Joomla the website no longer worked. I've got the following error message:
pms.uddeim.profilelink: UddeIM main component not installed.
And of course I wasn't able to install it again because of another error message
There was an error uploading this file to the server.
Maximum PHP file upload size is too small: This is set in php.ini in both upload_max_filesize and post_max_size settings of your PHP settings (located in php.ini and/or .htaccess file).
Unable to find install package
I've read another post in the forum in which Kyle mentioned
If that happens just unpublished the Private Message System plugin. Sounds like it was enabled when UddeIM wasn't installed. Aside from that I'm not sure else could cause that unless maybe the UddeIM CB plugin was installed without the UddeIM component.
But of course I couldn't get to, because I get the same error message in the backend when trying to go to community builder ---> Plugin Management "pms.uddeim.profilelink: UddeIM main component not installed."
I was able to solve the problem by accessing the FTP and deleting manually the following plugins:
plug_pmsuddeiminbox
plug_uddeimblockingplugin
plug_uddeimprofilelink
You can find those plugins within the following path
components/com_profiler/plugin/user/