Yes I got the figures from Task Manager. I have seen this a few more times since first posting. And sometimes even soon after shareaza starts.. (running for only 30min or so). I run regular anti-virus and anti-spyware/malware sweeps.
Shareaza seems to get stuck once in a while (rarely!) for no visible reason. Maybe it is some sort of a house cleaning function that takes temporarily lots of memory and CPU? Rebuilding/defragmenting a database or something like that.