Can confirm, I think, that it is just the usernames that are incorrectly linked.
If I click on my IP address, even though it is displayed against 3 different usernames (including my own), it is always my own accesses that are listed. (Confirmed because I am the only one with access to IP-Tracker.)
Unless of course, you're actually seeing the issue directly in the db.
Happy to uninstall/install, but before I did that and potentially lost evidence, I tried looking at the Db.
First in IP_Tracker I did Host search on 1st 2 octets which listed my IP, with my nick on 626 hits, nothing/null (not logged in?) on 59, 4 on a user-only nick I use for testing, but also 11 other nicks (incl "Anonymous") which are not mine with between 1 and 4 hits each.
Those other nicks usually appear with their correct respective nicks, so the "error" is transitory in nature.
So in DB file _iptracking in phpmyadmin, I first sorted by ip_address, and then looked for layingback nick. Sure enough mixed in with the "layingback"s where Null, Anonymous, and each of the other - incorrect - nicks.
Does this rule out the theme, or could it still be a substituted .php somewhere. Using a refinement of my reDesign3+ but I've not added or removed any included .php or .inc files that I remember, so would expect it to be same as reDesign/redesigned - unless I've messed up, which is of course more than poss.
What should I look at/for next?
[ I thought it could be logged in as Admin and not User but I can see other users who are showing up with other IP's (in the wrong country). ]
Just to summarise for others reading this forum looking for solutions, the coding error was mine! :oops: And although the fix did show up a very minor issue with IPT, it was in a different area, not directly related to this problem.
Thanks to Phoenix for helping me focus on the correct issue.