Hi there - yes, 2.0 is not fully multisite compatible and is going to be very buggy on subblogs. It's on our agenda and we're fairly close to fully multisite compatibility, but coming back to that is just on hold until we get through the current slate of issues for normal, non-multisite installs.
Just FYI - 1.9.13 and other legacy versions prior to the latest big update were also not really multisite compatible and should have been very buggy if you tried to use them on sub-blogs.
@daisy - there's another beta update 2.0.11 available today. But if 2.0.10 didn't address, I don't suspect that will.
If that's still not working, I'd ask you to try one other thing. Can you please go to Settings > Permalinks and if you are using default permalinks, try another options like postname?
If that still doesn't work, either submit a bug report with login credentials and we'll take a look or, yes, roll back for the time being.