ok, I seem to have narrowed the problem.
We have just installed Bamboo IT Productivity pack and Bamboo Project Management Suite. These 2 products come with about 32 components (web parts, file share library, custom columns e.g. rating column etc).
There is some conflict with these components what that of SLK pages.
I would be getting in touch with the Bamboo Support to fix that. Please le me know in case you got any idea.
Else, I would have to shift all by SLK site collections to some other web applications where Bamboo Suites are NOT installed.