Whenever I use the vanish command other players are disconnected from the server. Since the plugin isn't officially supporting the current dev bukkit build this will give you time to tackle it until the recommended build comes out.

Error Log (right before other players are disconnected.
00:35:33 [WARNING] Failed to handle packet: java.lang.NullPointerException
java.lang.NullPointerException

00:35:19 [INFO] shinji2570 [/67.234.117.32:50055] logged in with entity id 1435 at ([world] 147.8080930508053, 70.0, 318.57500661222167)
00:35:31 [INFO] [VANISH] shinji257 reappeared.
00:35:33 [INFO] [VANISH] shinji257 disappeared.
00:35:33 [WARNING] Failed to handle packet: java.lang.NullPointerException
java.lang.NullPointerException
00:35:35 [INFO] Connection reset

Bukkit: 1492 (MC 1.0.0 bukkit dev)
Spout: 545

This plugin does not occur on bukkit 1337 using spout 510.

Thanks.

The full error shows that it isn't a vanishnopacket error but a spout error. :(

Aww.... So spout still isn't playing nice then. :(

Unfortunately I can't test spout 545 with vanishnopacket 1.8.3 on older bukkit 1337 because whatever they did also broke it's support for the current bukkit rb.

Versions of spout are built for specific versions. So, combining stuff in strange ways ends... poorly.

I'm a little disappointed in this error no matter whose fault, as it's going to result in a lot of server owners thinking this plugin sucks.

Also I'm going to close this for organization purposes, we can keep chatting if you'd like.

Yeah, it seemed to have been my fault this time ^_^

I noticed that you managed to find and fix (or workaround) the issue. Thanks! :)