This is a known bad bug in 1.1.1 - it will be fixed today or tomorrow in 1.1.2.
Sorry for the inconvenience.
If you want to work around it yourself, you need to create the 'options' table on your mysql database using phpMyAdmin or similar.
Then, add the following line to zp-config.php:
`$conf['server_protocol'] = 'http';`
Or just wait a very short while for 1.1.2, where we've fixed it. Sorry again for the inconvenience.