| Dave Justus |
There are no rules against it. It might take some retraining through, as some previous class features won't match (domains, channel energy etc.)
Some GMs might require additional role playing of the conversion process.
In general, I would think an evil god would be more willing to accept a formerly good cleric who was cursed to be evil than a good god would accept an evil cleric who was cursed to be good, but the is a personal opinion as well as being highly setting dependent.