Board Thread:Bug Reports/@comment-26057623-20150130075226/@comment-2158701-20150130182441

Technic Classic, not Tekkit Classic? Wouldn't know then, but I did have a similar problem  when I attempted loading my tekkit classic schematics into tekkit lite, with blocks not being there and whatever.

You mentioned something about an update. If you're talking about technic update, that may well be the problem. Reinstall the exact version of the game last known to work, and check if your world works there. No guarantee that your world isn't already corrupted though.

And lesson be learned, but I'll say it again, if you don't have backups of backups, your worlds will break eventually! Murphy's Law demands it! If you're actually talking about Tekkit Classic, i.e. the version this forum is about, then a very good idea would be to save your important stuff in WorldEdit schematics on a locally hosted server as well.