What Blender version does this happen with?

2.56a
And it doesn't happen with 2.49 on any fo the machines

Can you please try RC2 from http://download.blender.org/release/Blender2.57 ?

Kieran:

It's not that we don't believe you have problems, but the bug tracker is for verified & redoable cases we can work on.
There's a lot of reasons why Blender can't run on systems, and in many cases it has to do with local installs, drivers, opengl configuration, and so on.

No its fine, i understand what i said wasn't exactly "useful". Network rendering was removed from blender 2.57 anyway so it doesn't matter :P . (Blender's menu system was coursing the lockup so i couldn't start network rendering)

Network rendering hasn't been removed, but moved as an addon. This means you have to enable it in user preferences to be able to use it.

Well what ever the problem was it has been fixed now im using 2.57 works on 3 out of the 4 machines i have tried :)

glad the newer blenders work better for you :-)
For the system where blender stalls, you could still do further testing to see why, but mostly this ends up being hardware configuration in my experience, its unlikely a bug in blender.

If you can find some steps to redo a problem or more concrete info on this problem, open a new report.

closing this one.