Same here . . changing the prefix was easy but it didn't work. Changed it back to wp_ and it was fine. Another issue I noticed was how these McInstalls (Click and Blog!) of WordPress on my service at least, gives you zero control over the install procedure.
I tried a fresh install recently also and it was seriously screwed up. Permissions we're all messed up 12 outdated plugins I couldn't update or delete. An amateur wouldn't even notice this stuff.
I mean if the hosting service can't install a secure WordPress properly to begin with forget it.