G'day David,
A quick 'WHOIS' reveals that your IP is registered to Austin College. Most colleges operate 'proxy' systems so that everyone accessing the internet from that college will have the same IP address. The problem this presents is that if ANYONE in your college vandalizes Wikipedia, you will see the warning messages and suffer from the ban that has to be imposed. There isn't a lot that can be done about this - all you can do is wait for the ban to expire or try editing from a non-college computer
That won't be possible, as the IP was blocked indefinitely in September 2005.
The IP's contribs show only the one edit; it's unlikely that an entire university would produce only a single edit, and even if Austin only connected to the Internet in late 2005, the blocking would presumably have generated *some* complaint. As such ISTM that the entire University wasn't blocked, but rather one workstation, which Ms Sweat had the misfortune to edit from some months later.
There's very rarely a good reason to indefinitely block an IP address (only do it in cases of open proxies, or Raul's cunning "email me to get unblocked, school administrators" manoeuvre), and in this case the blocking admin almost certainly did not have enough information to make the "block forever" call like that. I'll take the issue up with him.