With PHAkT v1.0 some users are getting the following error when trying to create database connections :-
org/gjt/mysql/Driver - Class Not Found
This is happening because of the new JDBC connection type that PHAkT can utilize. In the Readme.txt within the original PHAkT archive it states that JDBC connections can be used, but a specific JDBC driver needs to be installed.
To resolve this problem download the MySQL JDBC Driver installer here. Install the extension using the UltraDev Extension Manager and then restart UltraDev, and the error should be resolved.