kmail single input?

[Petrus de Calguarium]

I'm using kdepim4.5.94.1-1.fc15 with kde-4.6.0.

Mostly, there are no problems with checking for emails, but every once in a 
while (1 out of 10 times or so), it just hangs for ages at the first of my 
various pop servers and then a window will pop up asking if I want to cancel or 
try single input or a third option.

What in tarnation is single input?

Whatever it is, it seems to work, afaict.