wordpress 3.1

before:

I click styles, twentyten theme is just one of Available Styles

after:

I relabel default theme folder twentyten to yoyo, and alter some value in fashion.cascading stylesheet, then click styles link, yoyo does not appear.

basically relabel yoyo to twentyten, then twentyten appear again.

PS: I check permission with yoyo, it's readable to everybody.