Is it intalled both on your client and server?
I don't really know if it was that. But now it works. I don't know how.
I started disabling every mod one by one (both on server and client, recreating a new server world each time). After I disabled Aroma Core and Aroma Backup, NEI was finally working . So I tried re-enabling just Aroma Core, NEI was still working. So I re-enabled Aroma Backup, and NEI was still working. Was Mobius/Opis activated or not before that? I can't rememeber.
I have it enabled on the server now, but disabled on the client, and NEI works properly. I let it disabled on the client because if it's enabled, the client crashes right after the loading of a world (single player or on the server).
I'm kinda frustrated that I can't be sure what was causing this bug.
But I'm tired of trying to figure it out since I'm on it for like 4 days now. Anyway it is working now, so I'm finaly gonna be able to play. NIce!
Thanks you very much for helping me!
There is another bug another guy was complaining about with Infinity, higher in the thread. The uncrafting table not working. You can not take out uncrafted stuff from it. I tried myself, I have the same bug.
But it works on Direwolf20 pack for instance. Can you use the uncrafting table yourself?