Players cant pick any items up

Hi,

On my bukkit server about 2 weeks ago, I came on and I couldn't pick any items that have been dropped, this is still a problem.

This happens to only a few players on my server.

I really need help ,Please Help.

Plugins:

Plugins (67): World Portal, Orebfuscator, CityWorld, MyCommands, GoinRound, Vault, uSkyBlock, VoxelGadget, SurvivalGames, Announcer, AntiAd, WhitelistMessage, SignShopHotel, RandomPlacer, Votifier, GameModeChanger, MobArena, GAListener, TimTheEnchanter, Citizens, Jobs, DigitalClock, DolphinSpleef, WorldEdit, NoCheatPlus, TagAPI, NameTags, MineStats, PluginReloader, PermissionsEx, ChatGuard, LogBlock, MyCommand, Paintball, LWC, WorldGuard, MineResetLite, EmergencyDowntime, CoreProtect, iDisguise, GameModeInventories, XRayLookup, Modifyworld, iProtect, ButtonWarp, CCTV Camera, MobHealth, SignPortals, Essentials, ServerSigns, Enjin Minecraft Plugin, PlotMe, Multiverse-Core, OnTime, EssentialsChat, ChatManager, EssentialsProtect, EssentialsSpawn, EssentialsGeoIP, BOSEconomy, EssentialsAntiBuild, pvparena, Factions, Multiverse-Portals, BattleArena, Lift, AntiCheat

Thanks