AylaAsperger

I had the same problem, when I tried to update forge beyond 1290. I kept downgrading untill I was back at version 1290, and that one still works with optifine. So untill optifine is updated to work with the newer forge versions I suggest you downgrade forge to build 1290.

Thanks for the official answer. I hope my favorite mod (spc) will one day also be a mods folder mod and then your solution (separate folder without jar/json) will be best. For now, making different versions AND different instances depending on the different versions will make things unneccessary complicated, so I'll keep it like I had it. Thanks for your quick reply and all info!

@LexManos: I tried that already, but the created instance with that method does not have it's own jar/json file, so it can't have its own jar mods. Thats why the solution in this quote sounded good to me. But if that doesn't work then I just have to wait and look for another solution. Thanks anyway!

Does this also work for the Config folder? And the Saves folder? That way I can have instances with separate jar mods, folder mods and mod configs. Changing the directory in the launcher will create different instances which use the same jar/json file so this subfolder in mods and config would make a better solution. Edit: I've created a mods/version/ map and dragged a mod in there but it didn't load that mod untill I dragged it to the mod folder itself. I'm running MC 1.6.2. Did I do something wrong?

I also came here to report the same bug. Now I too have switched back to build #735 and it does indeed seem to solve the problem. I realised the bug after falling to my death on some long ladders! I also found a temporary fix, if you (have to) stick to #738 for whatever reason: When you use an NBT edit on the level.dat file and remove the forge folder from it, ladders do work, however as soon as you close and reopen minecraft the issue returns. Unless you go to NBT edit again.....

Thank you very much, that makes everything clear! I have posted this link in the topic of one of these mods, so I hope that the mod author will read this and that he'll be able to solve the ID reassign and collision conflict with this! The only question that remains on my mind is how it is possible that Minecraft Forge chooses conflicting ID's for these two mods, I would think that should be impossible? And as I read the mod-topics I am not the only one that had that happening?

I alerted the mod author to this topic, but I do want to add something here. You say it would be solved if those default ID's are above 256..... in fact most of those default ID's are above that, but still ALL ID's, including the ones higher then 256, get auto assigned by forge. So how is that possible if the problem is only the low ID numbers?

Check this post by the mod author for the default ID's: Click!

Okay, but in the case of these mods it auto assigns conflicting ID's while there are default ID's in the sourcecode that aren't conflicting with each other. How is it possible that these default ID's are skipped and conflicting ID's are assigned? Because using these defaults not only prevents conflicts, but also world compatibility issues. And I would think when auto assigning ID's Minecraft Forge would at least check if it has assigned the chosen ID's already, but maybe something went wrong here?

I recently discovered that when I install mods that use Minecraft Forge, their block ID's are automatically reassigned by Minecraft Forge, and I ran into some issues with this feature. For example: When I update minecraft or for whatever other reason need to reinstall a mod, it reassigns block ID's again with other numbers then before. And when someone else installs the same mod they also get other ID's then I have. This creates map incompatibility, which can be very annoying. I understand that this is probably meant to avoid ID conflicts, but somehow in this case it rather caused an ID conflict that wasn't there in the first place. I installed SimpleOres and Netherrocks, both made by AleXndrTheGr8st, and their default ID's are perfectly fine in not conflicting with eachother. However each time Minecraft Forge reassigns their ID's they do conflict on a large scale, rendering many items from one of them unavailable. Therefore I would like to know if there is an option to disable auto reassiging ID's or if it would be possible to only reassign ID's when a conflict is found. Or even better, having Minecraft Forge ask what to do when it has found a conflict. I am currently running Minecraft v1.4.2 with Minecraft Forge Universal v6.0.1.349. I hope anybody can help me out with this, because I'd really like to be able to solve this!