On a SQL Server 2005 clustered - I set the maximum concurrent connections to 1 and now the SQL server cluster cannot start. I guess it needs at least two connections (one for each node).
Can I recover from this by restoring the master database?
You might not have to restore the DB, try these instructions first:
When you successfully connect to the instance of SQL Server 2005, execute the following Transact-SQL statements at the SQL Server prompt. sp_configure 'user connections', Go Reconfigure Go
Restart the SQL Server service for the change to take effect.