Version:            (using Devel)
Installed from:    Compiled sources
Compiler:          4.2.3 
OS:                Linux

Steps to reproduce:
1. launch konqueror or dolphin
2. connect to a ftp server (in my case vsftpd on kubuntu)
3. create two files foo.txt and bar.txt
4. select bar.txt and rename it to foo.txt

you won't get warned or asked if you'd like to suggest another filename, the file is just being overwritten and the most confusing thing: you see foo.txt twice unless you hit F5.