Indirect XDMCP doesn't work

[Alvin]

I'm having troubles with XDMCP

'$ X -query hostname' works. No troubles there.

'$ X -indirect hostname' shows a chooser, but when I choose the server (same 
hostname), I get to see a default grey background with an 'X' mouse pointer. 
After a while, I just get thrown back to the chooser.

Anyone an idea as to what causes this, because I want to see a chooser. There 
are multiple X clients on the network. The others are Solaris based and work 
fine.