Yes, I understand you perfectly, it seems that this issue arises only when you are at the border of filling your gfx card, the file is 128*something, so this size indicator is somewhat faulty. I tested it with only optifine and forge, and by my understanding of the compatibility(which is in place, since my friend is able to run this combination, she does have more memory as well), but it seems that hd textures when run in conjuncture with optifine AND forge overload the GFX memory much more. By taking a wild guess I'd have to say that some textures are loaded twice due to how forge works and how optifine works. And I know that you do not support this officially, but I wrote to the optifine creator and wanted to hear your opinion as well. If you have any additional ideas, throw them at me. Thanks for the reply tho.
The logs are above. Using latest Forge 1.7.10 1180, OptiFine_1.7.10_HD_U_A4(but tried all of them) and Sphax PureBDCraft 128*128 Resource pack I encountered some strange bug, I already researched it and asked the optifine developer about it, he mentioned you might be doing smth more with the texturepack. The thing is, this texture pack works while using optifine on all versions, and even while using only forge. But if I use forge in conjuncture with sphax in the latest one I get this error. I have previously used the same size texture packs and have not encountered this problem. Are you doing something additional with the textures or why is there an issue? Optifine only-----> works Forge only----->works Both-----> not