hmm...an update :) STP_displaySiteTagCloud() works but when a new blog is registered with no tags yet, just a post from Mr.Wordpress - site wide tag cloud starts showing "No tags found"
However, as the new blog posts a new post with any tag, the site wide tag continues to work....
strange...must be a thing that when a new blog is registered, there is no stp_tags table there yet, its only created when any post is tagged...will try to look into that
if anyone can help, please do so...tnx.