Naming a 'blog' subdirectory

Hi,

I installed WordPress MU as there are a couple of subdirectories I want to have the same theme and plugins as the ones on the root WP site, in order to avoid me having to repeat the processes over and over.

My main site on root uses WordPress as a CMS, but I also want to use the same theme for my blog, and I want to name the subdirectory for this as ‘blog’, which I am having trouble doing.

As soon as I try to name it blog, I get the following message:
‘The following words are reserved for use by WordPress functions and cannot be used as blog names: page, comments, blog, files, feed’.

Iven went into options under Super Admin and removed blog from the banned list but this never helped.

Surely this must be possible as I am sure there are others who do a similar thing? I have Googled the issue and searched in WordPress forum but cannot find similar issue.

Also, although the theme will be the same, the logo and perhaps the colours will be different than those on the root site. Everything else will be the same though. Is this possible, or should I just install a single WordPress in the blog subdirectory?

Thanks.

Stuart