Took me awhile, but I voted for the Yoshi soccer one.

Back to lat03, I didn't just check IPs.  I'm aware that people have siblings which use the same IP.  Also, people in the same area on a dynamic IP can end up showing the same IP.
I checked other things before making my decision, such as behavior, registration times and so on.  I could check the raw access logs if I wanted to see what exactly was done, but I have better things to do :P
Your case is possible, but not plausible.

I don't want to act as someone telling you what you should do or not do, so I really think wee should forget this incident and move on.  I think you should be allowed to enter next week's competition, but the ultimate decision is up to tigerfan.  At least you're aware of this issue, and hopefully won't do it again :P

Sorry for any inconvenience/disturbance caused.
Regards.

=D