I'm running 4.3.4 on Debian Squeeze. I just started my computer, launched Konqueror... and my directory tree is gone! how do I get it back? Adding insult to injury, it won't do ftp logins now either. What just happened?

Update... I wound up rebooting my box and the ftp logins are now working. But my directory tree view is still missing... which means my file manager is essentially useless. Where did it go?

Please try running "kbuildsycoca4 --noincremental" then logout and back in again.

That fixed it. What happened, exactly?

The Sycoca is essentially a cache of information regarding the application and plugins installed, what mime types they support, what protocols are available over KIO, etc on your system.

As such, whenever it is damaged or loses entries, applications can lose functionality or break entirely if it doesn't contain a exact representation of what is actually installed.

In this case, the entires referring to the FTP KIO slave and the Tree view plugin for Dolphin/Konqueror were damaged or mistakenly removed from the Sycoca. That command rebuilt it, ignoring the current content of the cache and ensured it now has an accurate representation of your system and thus restored the functionality.