I am using FTB's Crackpack modpack am having trouble running it. I wanted to add optifine to help my game but it is conflicting with a mod. I have version 1.1.0 of crackpack and i have added Ars Magica 2 version 1.4.0.009 and AnimationAPI version 1.2.4 (Minecraft is version 1.7.10) The version of optifine i am trying to add is Optifine HD_A4.
Could you please define conflicting? Is this a graphical anomaly? If the answer is yes, my recommendation is to turn off fast renderer (or is it fast math, check them both). Also, threaded chunk loading just seems to cause all sorts of problems, just go with the normal chunk loading until you get everything playing nice. Also, that sounds like a pretty old version, I'm using OptiFine_1.7.10_HD_U_D6 in mypack Ascension of the Technomancer. It contains over 300 mods and I'm having no compatibility problems with Optifine, although I think if I take a newer version than that, it will start fighting with Fastcraft and NotEnoughIDs (literally so many mods I blew out the block ID limit and needed a fix). So it's probably a settings issue, if you have changed anything off the default, you can start clean by deleting minecraft/optionsof.txt (file, not folder obviously). Beyond this, it's pretty hard to give more specific advice without knowing the kind of compatibility issue your having. Hopefully, these pointers will guide you a bit.