It used to be that when i added a new torrent the add torrent dialogue window would have an option of which category to assign the torrent to. I no longer see this option, and I'm not sure if I've done something wrong in creating the categories, or if this was a change in a recent update. I can still set category's manually after the torrent has been created but there's no way to do it from inside the add torrent window anymore

I can set categories in Tix 2.51, loading torrents, etc; I don't know what could be; pretty chance of your settings.

I'm on 2.53 64-bit version, any clues as to what setting i might have goofed?

Hello. It would be easier if you provide a screenshot.