ok, head over her: http://pacura.ru/2006/08/03/buddha-temple/ that is my personal test site so far. check out the source code, you'll find these lines:
<meta name="description" content="This is the Wat Phra Yai - the Big Buddha Temple from Koh Samui one of the most beautiful islands of Thailand. ">
<meta name="keywords" content="asia, big buddha, koh samui, temple, thailand, travel, pictures">
this is what I added with the plugin I mentioned above, it gives you the option of adding descriptions and keywords while posting.
Now check out this example where its not working: http://sibiu.zice.ro/tag/vali-barbulescu/
The only meta relevant thing you'll find here is this:
<meta name="description" content="Just another Zice.ro weblog">
This comes from another plugin that just takes the first few sentences of the posts content and makes it into a description tag. And NO there is no interference between these 2 plugins, on the site I mentioned above both are working together using wp 2.0.5
The thing is the automatic description generation is fine if you post has content, but if it does not have, like my photo-only posts I have to enter the description manually. Thats where the second plugin comes handy.
And now I realized the plugin I have problems with seems not to work with wpmu...
I hope this was enough detailed info so you can have a look and give me some hints.