Blogs give a blank page/posts are in the 'main site's ' blog, not author's own

Hello all.
I’ve had a wordpress site (mafgirl) for yonks, but am fairly new to WPMU (a few months) I’ve got a social network (driverszone)about to launch next month and am just ironing out little niggly bits.
I am struggling to get my head around the multi blog thing. All users at the moment are test users created by the owner and me, we are both super admins and the test users contributors. as super admin eleanor I have created groups (Car Clubs in our network) with a blog, the super admin James has created the site blog and our two virtual users have created test blogs. None of these blogs are accessible as they all turn out a blank page. I read somewhere on a forum that maybe they need to be verified via email, but no emails have been received.
Furthermore, when I had the virtual user marjolijn create a post via dashboard, it was pending..
I wasn’t sure how to approve a pending post, apart from editing it and clicking publish. This how now resulted in the post being published in driverszone main blog, rather than the virtual author marjolijn’s ‘another test’ blog. The post itself is accessible by clicking the link to the post on the website’s Blog Page but ANY of the blog links give a blank page.

Sorry for the long story, I hope someone will know what it is and it is probably something really simple in the settings..

PS I use WPMU 3.1 and BuddyPress 1.2.8 (with the Theme Buddy Builder by Patrick Cohen)

Thanks!