Adarcer

ok thanks will do that

No with just forge installed on a separate instance it works as expected.. was kinda hoping someone would know what mod was causing the problem or a possible mod conflict, as the error does not say what mod is causing the error. or some type off error message explanation page, that might give me a clue on what is causing the error. like for example is it a mod with worldgen, or a mob that i can disable, or a mod i can just outright remove.

The thing in spoilers ... was a truly fresh world and was the end of the log when i pushed the button on client that would attempt too load the world anyways (either yes or no, one takes you back too menu) ... can tell by the save name. the crash log had the right date and time, what seems funny too me is this is supposed too be a single player test world instance not a server instance. for some reason new games are being seen as old games... seem too have found a way around this i have to copy and paste the level.dat into another folder rename it to level.dat_old and move back into save folder... then new world loads up after the error message ... but that is extremely annoying too have too do any idea on how too fix this problem

sorry that was newest crash log cause i pushed the button that took me back too menu instead,here is the tail end of the crash log while trying to create a new world. just need advice on what I need to do the crash log does not tell me which mod if any is causing the problem crash-2017-12-13_18.37.21-server.txt

Was hoping someone could help me I am making a modpack and need too create a new world at times too check orespawn, biome decoration spawn, dungeons , lakes etc, but every time i try too create a new world i get this error "Forge Mod Loader detected that the backup level.dat is being used" I can get into old world by renaming the level.dat_old so forge cannot find it, but new worlds are blocked. have tried making a new instance in multimc, and still had same problem. latest.log crash-2017-12-12_21.12.00-server.txt