Please make sure you are posting in the correct place. Server ads go here and modpack bugs go here
The FTB Forum is now read-only, and is here as an archive.
To participate in our community discussions, please join our Discord! https://ftb.team/discord
It's not finding the FML classes it's looking for. This probably means one of the mods you added was made for a version of Forge sufficiently different from the one that comes with Infinity. Make sure you're running versions of those mods for Minecraft version 1.7.10. If you are, either update Forge (can't say I really know how to do that; you might be able to try copying over all the mods to a MultiMC instance and choosing which version of Forge to run?) or try slightly older versions of the mods you added.