GZDoomBuilder issue

You did nothing wrong, it's just that AMD fucked up the latest drivers somehow. Just roll them back and wait for the next update which will (hopefully) solve the issue.

So the sprites aren't appearing in-game, basically? Have you tried running any of the IWADs to make sure enemies and items show up?

Just now, KVELLER said:

So the sprites aren't appearing in-game, basically? Have you tried running any of the IWADs to make sure enemies and items show up?

Have I ran DOOM/DOOM 2 itself? Last time I checked it did work, I'll give it a go right now. 

3 minutes ago, kc101010 said:

Have I ran DOOM/DOOM 2 itself? Last time I checked it did work, I'll give it a go right now. 

DOOM 2 also appears to have this issue

Edit: So does The Ultimate DOOM, maybe FINAL DOOM might be affecting it

I'll thow a guess and say that you have an AMD card and recently updated your drivers.

Just now, KVELLER said:

I'll thow a guess and say that you have an AMD card and recently updated your drivers.

Yup... What have I done?