Pressing the back and forward buttons between two ftp directories uses
up more and more unix domain sockets and kioslave processes:

$ /usr/sbin/lsof | grep kioslave | grep unix | wc -l
520

4 back and forward button pressings later:

$ /usr/sbin/lsof | grep kioslave | grep unix | wc -l
1213

$ ps auxw | grep kioslave | wc -l
48

This is on a single user system.

Closing that kfm window doesn't close the sockets.

Try the url ftp://ftp.hogia.net/ and press on the bin URL for example.

When the unix domain sockets are used up, the X server can't accept any
more local X clients and it becomes hard to figure out what is wrong...