World: r3wp

The problem could be this as well: http://dev.mysql.com/doc/refman/5.5/en/old-client.html

when you upgrade your mysql server from 4.x to 5.x the passwords 
in your "mysql" table for users stays old, which hashed a different 
algorithm.. so you cannot connect it using username/password anymore.

I think the link didn't work because I discovered it was a moderated 
thread.

Doc, what a lifesaver! I just spent the last 7 hours trying to figure 
out what was wrong with my remote rebol-based mysql app. It stopped 
working after I upgraded mysql. I spent most of my time messing around 
with mysql until I narrowed it down to the protocol.
 
sql-protocol-41.r Addresses: 

User Error: ERROR 1251 : Client does not support authentication protocol 
requested by server; consider upgrading MySQL client  (When using 
newer long hash passwords) 
and

User Error: ERROR 1043 : Bad handshake  (when using older short hash 
passwords) 

Thank you for posting this. I was getting to the point of panic.

Glad to hear that my driver helped you solve your issue. :-)