to fix the problem, open the Technic Launcher then click on the Options button underneath the Login button. in the Options menu, there is a Clear Cache button that you need to click. clearing the cache pretty much just deletes the minecraft.jar file so the launcher can reinstall it with the new mods. once you've cleared the cache, choose the mod pack you want to use then login like normal and wait for the pack to download. you may need to repeat for other mod packs that you haven't installed before now, but i haven't tried to use other packs yet