ssh key / upload problem on new PC

[Thomas Wolff]

Hi,
I'm about to upload mintty 3.4.7 but I'm getting a "Host key 
verification failed." error.
Trying this on a new machine; I copied the whole ~/.ssh folder from my 
old machine, something that used to work in the past. It still works 
from the old machine (as confirmed by fallback for uploading mintty 3.4.6).
Does anybody have an idea what might be going wrong? Do I need a new ssh 
key? (But porting the key worked before...)
Thanks
Thomas