[dentin]

I'd recommend Alter Aeon. I'm a pretty casual player myself, and I've worked specifically on having a short startup time between logging in and playing. The solo play aspect is good, and grouping isn't that common until you reach higher levels.

The only down side is that it's not RP heavy. The introductory quests have a solid storyline and should last more than a few hours, but few people actively roleplay it.

-dentin