Okay, so ever since I installed a large amount of mods at once, my forge versions stopped working. Even after I took out the mods. So when I try booting up forge even with out any mods installed, the launcher is not working correctly. However, any other version such as optifine, or just vanilla mc, works perfectly fine. I had 60 mods installed, and I am usually able to play with 60+ fps. Please help! Btw I am on a mac, and this has never happened to me on this computer before. 

This has also been happening to me D: I tried removing the mods and I've redownloaded Forge both recommended and latest (before I usually used latest). This happened after I tried to get Rei's Minimap, so maybe I did something wrong, but I'm not sure why my Minecraft launcher just kinda blinks when I press play. I get this in the development console: [19:43:13 INFO]: Client> [19:43:13] [main/ERROR] [FML]: There is a binary discrepency between the expected input class bah (bah) and the actual class. Checksum on disk is 2db9307, in patch afcc0c32. Things are probably about to go very wrong. Did you put something into the jar file?

[19:43:13 INFO]: Client> [19:43:13] [main/ERROR] [FML]: The game is going to exit, because this is a critical error, and it is very improbable that the modded game will work, please obtain clean jar files.

[19:43:13 ERROR]: Game ended with bad state (exit code 1)

[19:43:13 INFO]: Deleting C:\Users\Anthony Chen_2\AppData\Roaming\.minecraft\versions\1.7.2-Forge10.12.1.1063\1.7.2-Forge10.12.1.1063-natives-5761891001923

[19:43:13 INFO]: Ignoring visibility rule and showing launcher due to a game crash

 

I was gonna make a post myself, but I kept reading the rules and EAQ, and kept getting paranoid I'd be banned

I have a similar problem to you, only it's not crashing. when i press play, the launcher disappears like it should, but it just doesn't launch mc, and then the launcher comes back.

Check the development console. At first I wasn't sure what was going on, but then i saw that it crashes kinda while trying to start with Forge, which makes it disappear for a sec then reappear.

[19:43:13] [main/ERROR] [FML]: There is a binary discrepency between the expected input class bah (bah) and the actual class. Checksum on disk is 2db9307, in patch afcc0c32. Things are probably about to go very wrong. Did you put something into the jar file?

 

You've modified you jar.

Delete the 1.7.2 folder in /versions/

and the Forge folder.

Re-run vanilla 1.7.2 then re-install Forge.

WOOT! It worked Thanks a lot for your help 

Thanks so much! These forums are great! If I ever need help with forge again, I'm coming right here! 

Wait, it works for 1.7 but i followed the same steps but it didn't work for 1.6. (I deleted the 1.6 files) 

Wait, it works for 1.7 but i followed the same steps but it didn't work for 1.6. (I deleted the 1.6 files) 

post logs

[19:43:13] [main/ERROR] [FML]: There is a binary discrepency between the expected input class bah (bah) and the actual class. Checksum on disk is 2db9307, in patch afcc0c32. Things are probably about to go very wrong. Did you put something into the jar file?

 

You've modified you jar.

Delete the 1.7.2 folder in /versions/

and the Forge folder.

Re-run vanilla 1.7.2 then re-install Forge.

This didnt work for me. I'm having this problem with forge 1.7.10. Do you have any solutions?

[19:43:13] [main/ERROR] [FML]: There is a binary discrepency between the expected input class bah (bah) and the actual class. Checksum on disk is 2db9307, in patch afcc0c32. Things are probably about to go very wrong. Did you put something into the jar file?

 

You've modified you jar.

Delete the 1.7.2 folder in /versions/

and the Forge folder.

Re-run vanilla 1.7.2 then re-install Forge.

 

But what if I want to install optifine without using the installer? Like not using the optifine profile and using it with forge.