I did that and the line where it says something about 'banned':
2012-02-22 20:56:54 LOG_ERR: [bibliotekr.dk:30819.a8932c46 POST /status/main/register] ServerErrorAction: 500 You have been banned from subscribing.
Thanks for the suggested solution which help me a bit!
Now the previous error has gone but ... a new one is occuring now:
"You have been banned from subscribing."
? I haven't set this banned thingy anywhere, I think...
@n4rky If I understand your question correctly ... then you should use the Recaptha-plugin which you find in /plugins/Recaptha - read the README file which explains pretty straight forward how to use it.