I just recently updated my tekkit as well, and couldn't log into my favorite tekkit server, and also got a list of mods I needed.
mod_IC2 v1.95
mod_Tubestuff 48.2.1
mod_Ironchest 3.3
mod_CompactSolars 2.2
mod_ImmbisCore 48.2.1
mod_Railcraft 5.2.4
mod_ICNuclearControl c1.1.6
mod_CraftingTableIII (Beta1.8, MC1.2.5)
I tried using the Backup folder in Tekkit to see if it would reverse it, but after logging in from the launcher it would crash.
I had to uninstall everything and then redownload the client, but I believe it no longer has the backup of the previous version.
Anyone have a file backup of the previous version, and what did I do wrong trying to revert to the old version?