I've just encountered what might be a pretty serious bug in Teracopy.
I was updating some CD writing related utilities (cdspeed.exe, drivespeed.exe, infotool.exe) and downloaded and unzipped the latest versions on my desktop. I then dropped cdspeed.exe to the folder where the original was located. Instead of giving me an overwrite warning, Teracopy just popped up the copy box and closed it - it didn't overwrite the file, it basically didn't do anything. I know for certain the utility wasn't locked by any other process. After fiddling around a bit it seems to me that Teracopy will not do anything if the exe file being overwritten is different. If it is identical to the file trying to overwrite it, it works normally & pops up the overwrite warning. I'm not sure if this'll be replicated on other systems but it seems likely.
Not sure how did you get this result, perhaps file was locked. Version 1.2 detects locked files well and even allows you to view locking process.
In any case, if this is serious bug, you should send message to the technical support first. I can fix TeraCopy errors, not people on the forum. If bug is really serious, I'll fix it and upload new version on the website right after I read about this bug.
Thanks to LifeHacker and other sites, more then 30 000 people downloaded TeraCopy by now, and no serious bugs was reported. A lot of changes was made in versions 1.1 & 1.2, based on user support tickets, including Unicode support.