Before 1.2.0, when I edit a file, I can upload a new file to instead the old one, but in 1.2.0 beta, I can not upload a new file.

I suggest 1.2.0 should keep this function.

Yes you can. It's hidden by default with a link that says "Click here to upload a new file". It was changed as a lot of users were apparently confused and thought they HAD to upload a new file when they edited a file - now the upload field is just hidden by default with a link to expand it.

Since I know you use Chinese on your site, make sure you added the new language strings to your Chinese language file (lang_downloads.php)

Thanks, bfarber. Glad to know you are still here, I was worried you might leave IPS...

I select English, the missing strings shew up. Hope there will be a good way to resolve the localization string missing problem. Everytime after I upgrade, comparing and editing the language files is a very painful thing to me.

Unfortunately that's an IPB limitation at this time. In a future release we'll try to make it easier for localization, but right now the only option is to carry over the new strings to your customized language file.