I also want to know if there are any solution to see the IP address of someone using a pseudonym.
Put your mouse over the pseudonym on RecentChanges and wait a second.
Maybe these pages can help you, but I have no clue about these things:
http://www.usemod.com/cgi-bin/wiki.pl?Actions http://www.usemod.com/cgi-bin/wiki.pl?AdminFeatures
Kurt