after Xorg update to 6.8 (I think) some of X applications wont run from a remote host using ssh -X, running xclock is okay but for example Metaphase does not run anymore, this is a big problem because I'm using it at work.
A friend of mine having same problem using same application running from gentoo so this is not an arch issue.
Now we do tunnel vnc to a local port from a solaris machine and from there starting the application, little bit to tricky for normal use I think.
after Xorg update to 6.8 (I think) some of X applications wont run from a remote host using ssh -X[...]
Maybe your problem is related to this.
I haven't used ssh in a while but what's talked about in that thread makes sense, and is probably related to your xorg update awhile back.