I downloaded and activated the contact form 7 (version 2-4-5) from within WordPress 3.1.2. Right after activation I couldn't access the dashboard anymore and got a '500 Server Error' (on /wp-admin/) instead, also when trying to login again.
Not knowing much about what I'm doing here, I couldn't find a solution to this. But at least found a way to access my dashboard again:
- use FTP to rename the plugin's folder, so that WordPress can't find it anymore and disables it automatically
- access to the dashboard is possible again now
(- I then changed the folder back to it's original name and deleted the plugin with WordPress)
For now I'm glad I can access my backend again. It's a pity though that the installation didn't work for me. If anyone would know a simple solution to this, I would be glad to hear it.
Otherwise, the above might help someone experiencing the same problem.