[Evolution] I/O error after upgrade

["Meesters, Christian" <meesters uni-mainz de>]

Hoi,

two days ago I did the upgrade to Ubuntu 7.10. Everything is working fine - except for Evolution.

I was used to see all my mail folder below "On This Computer", but now there is an additional top-level with 
my account name and various sub-folders, which I never created (default folders). When pressing Send/Receive 
I merely get the message:

Error while performing operation.
Could not connect to <server name>: Input/output error

Could not connect to <server name>: Input/output error

(The message is there twice, indeed.)

Does anybody know what might cause this error? The funny thing is that I do get new emails - in this new 
account I never created. Is there a way to merge these folders so that I end up with only one account below 
"On This Computer" again?

Things I already tried: deleting home/.gconf/apps/evolution deleting evolution itself and re-installing. 
Nothing so far helped.

TIA
Christian