This has been brought up by someone else, but it turned out it was a problem with the perm plugin they were using.

When I type /vanish, it brings up /vanish [on:off]. Basically, it won't allow me to vanish.
This began happening after the 1.5 release. All the permissions are the same, haven't been touched. No errors come up in the console or in the server logs.

Im using PermissionsBukkit.

enable permtest in the VNP config.

/vanish reload

/permtest vanish.vanish

I did what you said above
When I type "/vanish reload", it gives me the "/vanish [on:off]"
So i just reloaded the whole server
When I type /permtest vanish.vanish, it tells me "unknown command...."

So a no go on this one.