Archive type error with SLADE

[CoyoteComrade]

Whenever I try to open a mapset I've been working on for a while in slade, it says unsupported or invalid archive format. That doesn't make any sense to me, I havent messed with it outside of slade. Any ideas?

[Gez]

Is it a wad or a zip/pk3?

 

if zip, can you open it with 7-zip or other?

 

There should be backup files. You can try renaming the most recent to something else and see if it opens.

[CoyoteComrade]

It's a wad. The .bak files only give me markers when I try to load them