WordPress MU

My permalink structure is this:

/blog/%postname%/

When someone visits mydomain.com/blog or mydomain.com/blog/, they get a WordPress-managed 404. I'd like them to be redirected to mydomain.com.

1) I tried using .htaccess like this:

Redirect /blog http://mydomain.com/

But that breaks all my permalinks like this:

http://mydomain.com//%postname%/

2) I tried this:

Redirect 301 /blog http://mydomain.com/

But that had the same result.

Any suggestions? Thanks!

The /blog/ is stuck in there on subfolder installs.

The cleanest way to handle it is to write a new page called Blog. No text.
Then go to Settings -> Reading and set that as the "show posts page".

no, it doesn't redirect. But it no longer gives a 404.