At the moment, there's a bug after we upgraded all the server software. It seems vBulletin and the current version of PHP don't interact all that well.
As such, when you go to edit posts which have special characters outside the standard alphabet and punctuations (such as the é in Pokémon, Japanese text and so forth), it brings the edit box as blank.
We're working on a work-around but it likely won't be live til later today. In the mean-time, just make sure to copy the post you wish to edit, just in case. Thankfully, you can cancel the edit so it doesn't save the post as blank.
Just figured I'd give you a heads up while we fix