BES Express 5.x will not install
 

I have SBS 2003 and am trying to re-install BES Express 5.0.3, however, the install fails almost immediately!

I get as far as selecting 'English' and continuing when selecting BESAdmin and the domain. Then I get the 'bar' going across the screen and then disappearing when it gets half way!

I've gone through the following at least a thousand times...... (or it seems like it)

I've been trawling the forums for 2 days now and following dozens of recommendations without success.

My BESAdmin account is an administrator of the server (local admin) but is not a domain admin (I've tried that).
I have SQL 2005 and 2008 installed (running other things).
I've stripped all mention of RIM from the registry.
I've removed all mention of RIM from folders in 'Program Files' etc.

I'm open for suggestions.... please.