Emacs not redisplaying

[Henrik Jegbjerg Hansen]

I have a problem with Jabber and ERC.  At first I thought it was
jabber-specific, but since it also happens with ERC, it must be more
general:

When I sit idly in Emacs (or use firefox, for example), and touch
nothing in Emacs -- messages in ERC and Jabber does not show up, and I
get no notifications of any kind, in the mode line or echo area, or
anything.  Only when I touch a key (e.g. C-f) in Emacs do they come, all
at once.  

How can this be?  And how can I fix this problem?

Thanks,
Henrik Jegbjerg Hansen