Have you tried narrowing down the cause by starting a new game with no mods or texture packs and then adding the mods/packs one by one until the problem re-emerges?
If you want other people to help you troubleshoot, you will need to provide a lot more information. For example is this a Java singleplayer game? Did it use to work fine and then suddenly get corrupted? What OS version are you using?
Edit: Oops, can’t be a singleplayer game if you are using PVP mods. Are you playing on your own server and do other players experience the same problems?