Hey,
BC 2.2.8 is an old version and was made for R1 not for R4. That could cause problems.
To be sure please check your server log (/serverdir/server.log) for errors. Client errors can be caught by starting Minecraft this way.
this is my server log when i try to join the server with quantum armor in my inventory
2012-02-21 10:19:21 [INFO] renderme [/10.0.0.4:3981] logged in with entity id 1484 at ([world] 214.5, 66.0, 216.8125)
2012-02-21 10:19:22 [INFO] renderme joined with mod_ModLoaderMp 1.0.0, mod_ReiMinimap v3.0_01 [1.1], mod_TooManyItems 1.1 2012-01-12a, mod_MinecraftForge 1.3.3.12, mod_BuildCraftCore 2.2.12, mod_BuildCraftBuilders 2.2.12, mod_BuildCraftEnergy 2.2.12, mod_BuildCraftFactory 2.2.12, mod_BuildCraftTransport 2.2.12, mod_IC2 v1.64, mod_RedPowerArray 2.0pr4d, mod_RedPowerCore 2.0pr4d, mod_RedPowerLighting 2.0pr4d, mod_RedPowerLogic 2.0pr4d, mod_RedPowerMachine 2.0pr4d, mod_RedPowerWiring 2.0pr4d, mod_RedPowerWorld 2.0pr4d
2012-02-21 10:19:22 [FINE] renderme joined with mod_ModLoaderMp 1.0.0, mod_ReiMinimap v3.0_01 [1.1], mod_TooManyItems 1.1 2012-01-12a, mod_MinecraftForge 1.3.3.12, mod_BuildCraftCore 2.2.12, mod_BuildCraftBuilders 2.2.12, mod_BuildCraftEnergy 2.2.12, mod_BuildCraftFactory 2.2.12, mod_BuildCraftTransport 2.2.12, mod_IC2 v1.64, mod_RedPowerArray 2.0pr4d, mod_RedPowerCore 2.0pr4d, mod_RedPowerLighting 2.0pr4d, mod_RedPowerLogic 2.0pr4d, mod_RedPowerMachine 2.0pr4d, mod_RedPowerWiring 2.0pr4d, mod_RedPowerWorld 2.0pr4d
2012-02-21 10:19:22 [INFO] renderme joined with mod_ModLoaderMp 1.0.0, mod_ReiMinimap v3.0_01 [1.1], mod_TooManyItems 1.1 2012-01-12a, mod_MinecraftForge 1.3.3.12, mod_BuildCraftCore 2.2.12, mod_BuildCraftBuilders 2.2.12, mod_BuildCraftEnergy 2.2.12, mod_BuildCraftFactory 2.2.12, mod_BuildCraftTransport 2.2.12, mod_IC2 v1.64, mod_RedPowerArray 2.0pr4d, mod_RedPowerCore 2.0pr4d, mod_RedPowerLighting 2.0pr4d, mod_RedPowerLogic 2.0pr4d, mod_RedPowerMachine 2.0pr4d, mod_RedPowerWiring 2.0pr4d, mod_RedPowerWorld 2.0pr4d
2012-02-21 10:19:22 [SEVERE] Could not pass event org.bukkit.event.player.PlayerQuitEvent to PermissionsBukkit
java.lang.IllegalArgumentException: Attachment cannot be null
at org.bukkit.permissions.PermissibleBase.removeAttachment(PermissibleBase.java:131)
at org.bukkit.craftbukkit.entity.CraftHumanEntity.removeAttachment(CraftHumanEntity.java:90)
at org.getspout.spout.SpoutPermissibleBase.removeAttachment(SpoutPermissibleBase.java:94)
at org.getspout.spout.player.SpoutCraftPlayer.removeAttachment(SpoutCraftPlayer.java:260)
at com.platymuus.bukkit.permissions.PermissionsPlugin.unregisterPlayer(PermissionsPlugin.java:137)
at com.platymuus.bukkit.permissions.PlayerListener.onPlayerQuit(PlayerListener.java:24)
at org.bukkit.plugin.java.JavaPluginLoader$2.execute(JavaPluginLoader.java:277)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:61)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:460)
at net.minecraft.server.ServerConfigurationManager.disconnect(ServerConfigurationManager.java:176)
at net.minecraft.server.NetServerHandler.disconnect(NetServerHandler.java:141)
at org.getspout.spout.SpoutNetServerHandler.disconnect(SpoutNetServerHandler.java:562)
at net.minecraft.server.ModLoaderMp.handleModCheckResponse(ModLoaderMp.java:466)
at net.minecraft.server.ModLoaderMp.HandleAllPackets(ModLoaderMp.java:128)
at net.minecraft.server.Packet230ModLoader.handle(Packet230ModLoader.java:179)
at net.minecraft.server.NetworkManager.b(NetworkManager.java:231)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:101)
at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:552)
at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:543)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
2012-02-21 10:19:24 [INFO] Connection reset