Board Thread:Questions and Answers/@comment-98.246.39.52-20121207020631/@comment-5584420-20121207045026

i believe its Tekkit 3.1.3 mods (i remember some version of tekkit 3.1.3 mods)

have you updated tekkit to 3.1.3 yet? (options,tick use development build,choose 3.1.3)

if its still happening,go  clear cache at options and redownload

if still happening too, get new launcher