Ok, solved... Took me some time to figure this out.. First, disabled every mod.. One by one.. When I finished with an almost vanilla copy of minecraft (only forge left and multipart) then I knew there was something weird going on.. Tried 3 different versions of java, no change.. Tried update libraries.. No change.. Tried downgrading forge.. No change... Downloaded another copy of monster but in 1.1.1 because i remember that worked well.. And it did, I had to change the folder to do it so it downloaded in another part of the disk, and thats when I realized that the problem was the hard drive. Don't know how am I so unlucky but FTB instalation just got into some corrupted place of my harddrive.. Solution? Format
THanks for your support all, but it was the most basic thing XD