This problem only occurs when on a server, since everything works fine in singleplayer. Using Forge .1231, a custom modpack, and hardcore ender expansion v1.6.4. The server is running on Cauldron 1.1231.01.207. When I join the server, everything works as normal, until I open my inventory and click my mouse button. It doesn't matter where I click, if I click, my game crashes. This effectively renders my game unplayable. When I open my inventory, I also don't see NEI, and I can't see it by pressing O(O hides NEI). Everything works fine in singleplayer, I can see NEI and I don't crash when I click.

Here is the crash-report: http://pastebin.com/S8fJRMzm

This is a game-breaking bug, so please look into this as soon as possible, thank you.

Cannot replicate on a Forge server with HEE + NEI and default configs. Everything works fine for me and the Resonant Rise team, who have a huge modpack also with HEE and NEI, so it's probably something specific to your pack.

I disabled HEE, and that fixed the issue with crashing when clicking. But I don't think that was the real problem. Problem is the NEI works fine in SSP and when I join my server with the same mods, NEI gets disabled or something. I posted the issue on the NEI github as well: Chicken-Bones/NotEnoughItems#117

This is the only error I get when I join the server: http://pastebin.com/8q944UVM
Do you have any idea what it could be? I've googled it numerous times, but I can't find any error like this one. You can probably go ahead and close this issue, just want to know if you have any idea what may be wrong. thanks

Well, extrautils seems to be creating broken items or something. I will add a check to HEE that will make sure NEI is enabled, that should fix the crash at least.